Biotechnological insights into extracellular enzyme production by thermotolerant fungi from hot springs and caves: Morphology, pellets formation, and protease production.

This study investigates the thermotolerant fungal biodiversity in caves and hot springs, focusing on their potential for extracellular enzyme production, specifically proteases. Samples were collected from the Cardonal region in Hidalgo, Mexico, using three different isolation methods. The study characterizes the morphological diversity of the isolated fungi and identifies various genera, including Aspergillus, Penicillium, Trichoderma, Cladosporium, and Fusarium, based on morphology. The isolated fungi were screened for their ability to produce extracellular enzymes on solid media, with a particular emphasis on proteases due to their industrial significance. Among the 35 isolated fungi, 20 exhibited proteolytic activity, and 12 strains were identified as good protease producers based on enzymatic index values. The study also evaluated the formation of fungal pellets by proteolytic fungi and found certain strains to display significant pellet formation. Additionally, protease production was examined by fungal pellets in submerged cultures, with isolate 6 demonstrating the highest protease activity. The findings highlight the diverse thermotolerant fungal biodiversity in extreme environments, and emphasize their potential for enzymatic production. This research contributes to our understanding of fungal ecology and provides insights into the biotechnological applications of these enzymes. The study recommends further molecular investigations to enhance biodiversity studies in such extreme environments.

Chitinase induction in Trichoderma harzianum: a solid-state fermentation approach using shrimp waste and wheat bran/commercial chitin for chitooligosaccharides synthesis.

This study innovatively employed solid-state fermentation (SSF) to evaluate chitinase induction in Trichoderma harzianum. Solid-state fermentation minimizes water usage, a crucial global resource, and was applied using shrimp waste chitin and a mixture of commercial chitin with wheat bran as substrates. Shrimp waste and wheat bran were pretreated and characterized for SSF, and the fungus's utilization of the substrates was assessed using spectrophotometric and microscopic methods. The resulting enzymes' ability to produce chitooligosaccharides (COS) mixtures was studied. Wheat bran/commercial chitin demonstrated superior performance, with a 1.8-fold increase in chitinase activity (76.3 U/mg protein) compared to shrimp waste chitin (41.8 U/mg protein). Additionally, the COS mixture obtained from wheat bran/commercial chitin showed a higher concentration of reducing sugars, reaching 87.85 mM, compared to shrimp waste chitin (14.87 mM). The COS profile from wheat bran/commercial chitin included monomers to heptamers, while the profile from shrimp waste chitin was predominantly composed of monomers. These results highlight the advantages of SSF for chitinase induction and COS production in T. harzianum, offering potential applications as dietary fiber, antioxidants, and antimicrobial agents. The findings contribute to by-product valorization, waste reduction, and the sustainable generation of valuable products through SSF-based enzyme production.

Fundaments and Concepts on Screening of Microorganisms for Biotechnological Applications. Mini Review.

Microbial biotechnology uses microorganisms and their derivatives to generate industrial and/or environmental products that impact daily life. Modern biotechnology uses proteomics, metabolomics, quantum processors, and massive sequencing methods to yield promising results with microorganisms. However, the fundamental concepts of microbial biotechnology focus on the specific search for microorganisms from natural sources and their correct analysis to implement large-scale processes. This mini-review focuses on the methods used for the isolation and selection of microorganisms with biotechnological potential to empathize the importance of these concepts in microbial biotechnology. In this work, a review of the state of the art in recent years on the selection and characterization of microorganisms with a basic approach to understanding the importance of fundamental concepts in the field of biotechnology was carried out. The proper selection of isolation sources and the design of suitable selection criteria according to the desired activity have generated substantial changes in the development of biotechnology for more than three decades. Some examples include Taq polymerase in the PCR method and CRISPR technology. The objective of this mini review is to establish general ideas for the screening of microorganisms based on basic concepts of biotechnology that are left aside in several articles and maintain the importance of the basic concepts that this implies in the development of modern biotechnology.

On the use of n-octyl gallate and salicylhydroxamic acid to study the alternative oxidase role.

The alternative oxidase (AOX) catalyzes the transfer of electrons from ubiquinol to oxygen without the translocation of protons across the inner mitochondrial membrane. This enzyme has been proposed to participate in the regulation of cell growth, sporulation, yeast-mycelium transition, resistance to reactive oxygen species, infection, and production of secondary metabolites. Two approaches have been used to evaluate AOX function: incubation of cells for long periods of time with AOX inhibitors or deletion of AOX gene. However, AOX inhibitors might have different targets. To test non-specific effects of n-octyl gallate (nOg) and salicylhydroxamic acid (SHAM) on fungal physiology we measured the growth and respiratory capacity of two fungal strains lacking (Ustilago maydis-Δaox and Saccharomyces cerevisiae) and three species containing the AOX gene (U. maydis WT, Debaryomyces hansenii, and Aspergillus nidulans). For U. maydis, a strong inhibition of growth and respiratory capacity by SHAM was observed, regardless of the presence of AOX. Similarly, A. nidulans mycelial growth was inhibited by low concentrations of nOg independently of AOX expression. In contrast, these inhibitors had no effect or had a minor effect on S. cerevisiae and D. hansenii growth. These results show that nOg and SHAM have AOX independent effects which vary in different microorganisms, indicating that studies based on long-term incubation of cells with these inhibitors should be considered as inconclusive.

Rapamycin induces morphological and physiological changes without increase in lipid content in Ustilago maydis.

The evolutionarily conserved serine/threonine kinase TOR recruits different subunits to assemble the Target of Rapamycin Complex 1 (TORC1), which is inhibited by rapamycin and regulates ribosome biogenesis, autophagy, and lipid metabolism by regulating the expression of lipogenic genes. In addition, TORC1 participates in the cell cycle, increasing the length of the G2 phase. In the present work, we investigated the effect of rapamycin on cell growth, cell morphology and neutral lipid metabolism in the phytopathogenic fungus Ustilago maydis. Inhibition of TORC1 by rapamycin induced the formation of septa that separate the nuclei that were formed after mitosis. Regarding neutral lipid metabolism, a higher accumulation of triacylglycerols was not detected, but the cells did contain large lipid bodies, which suggests that small lipid bodies became fused into big lipid droplets. Vacuoles showed a similar behavior as the lipid bodies, and double labeling with Blue-CMAC and BODIPY indicates that vacuoles and lipid bodies were independent organelles. The results suggest that TORC1 has a role in cell morphology, lipid metabolism, and vacuolar physiology in U. maydis.

New Insights of Ustilago maydis as Yeast Model for Genetic and Biotechnological Research: A Review.

The basidiomycete Ustilago maydis is a biotrophic organism responsible for corn smut disease. In recent years, it has become one of the most promising models for biochemical and biotechnological research due to advantages, such as rapid growth, and easy genetic manipulation. In some aspects, this yeast is more similar to complex eukaryotes, such as humans, compared to standard laboratory yeast models. U. maydis can be employed as a tool to explore physiological processes with more versatility than other fungi. Previously, U. maydis was only considered as a phytopathogenic fungus, but different studies have shown its potential as a research model. Therefore, numerous promising studies have focused on deepening our understanding of the natural interactions, enzyme production, and biotechnological capacity. In this review, we explore general characteristics of U. maydis, both as pathogenic and "innocuous" basidiomycete. Additionally, a comparison with other yeast models focusing on genetic, biochemical, and biotechnological research are analyzed, to emphasize the versatility, dynamism, and novelty that U. maydis has as a research model. In this review, we highlight the applications of the yeast form of the fungus; however, since the filamentous form is also of relevance, it is addressed in the present work, as well.

Lipid droplets accumulation and other biochemical changes induced in the fungal pathogen Ustilago maydis under nitrogen-starvation.

In many organisms, the growth under nitrogen-deprivation or a poor nitrogen source impacts on the carbon flow distribution and causes accumulation of neutral lipids, which are stored as lipid droplets (LDs). Efforts are in progress to find the mechanism of LDs synthesis and degradation, and new organisms capable of accumulating large amounts of lipids for biotechnological applications. In this context, when Ustilago maydis was cultured in the absence of a nitrogen source, there was a large accumulation of lipid bodies containing mainly triacylglycerols. The most abundant fatty acids in lipid bodies at the stationary phase were palmitic, linoleic, and oleic acids, and they were synthesized de novo by the fatty-acid synthase. In regard to the production of NADPH for the synthesis of fatty acids, the cytosolic NADP+-dependent isocitrate dehydrogenase and the glucose-6-phosphate and 6-phosphogluconate dehydrogenases couple showed the highest specific activities, with a lower activity of the malic enzyme. The ATP-citrate lyase activity was not detected in any of the culture conditions, which points to a different mechanism for the transfer of acetyl-CoA into the cytosol. Protein and RNA contents decreased when U. maydis was grown without a nitrogen source. Due to the significant accumulation of triacylglycerols and the particular composition of fatty acids, U. maydis can be considered an alternative model for biotechnological applications.

Response of Ustilago maydis against the Stress Caused by Three Polycationic Chitin Derivatives.

Chitosan is a stressing molecule that affects the cells walls and plasma membrane of fungi. For chitosan derivatives, the action mode is not clear. In this work, we used the yeast Ustilago maydis to study the effects of these molecules on the plasma membrane, focusing on physiologic and stress responses to chitosan (CH), oligochitosan (OCH), and glycol-chitosan (GCH). Yeasts were cultured with each of these molecules at 1 mg·mL-1 in minimal medium. To compare plasma membrane damage, cells were cultivated in isosmolar medium. Membrane potential (Δψ) as well as oxidative stress were measured. Changes in the total plasma membrane phospholipid and protein profiles were analyzed using standard methods, and fluorescence-stained mitochondria were observed. High osmolarity did not protect against CH inhibition and neither affected membrane potential. The OCH did produce higher oxidative stress. The effects of these molecules were evidenced by modifications in the plasma membrane protein profile. Also, mitochondrial damage was evident for CH and OCH, while GCH resulted in thicker cells with fewer mitochondria and higher glycogen accumulation.

The basidiomycete Ustilago maydis has two plasma membrane H⁺-ATPases related to fungi and plants.

The fungal and plant plasma membrane H⁺-ATPases play critical roles in the physiology of yeast, plant and protozoa cells. We identified two genes encoding two plasma membrane H⁺-ATPases in the basidiomycete Ustilago maydis, one protein with higher identity to fungal (um02581) and the other to plant (um01205) H⁺-ATPases. Proton pumping activity was 5-fold higher when cells were grown in minimal medium with ethanol compared to cells cultured in rich YPD medium, but total vanadate-sensitive ATPase activity was the same in both conditions. In contrast, the activity in cells cultured in minimal medium with glucose was 2-fold higher than in YPD or ethanol, implicating mechanisms for the regulation of the plasma membrane ATPase activity in U. maydis. Analysis of gene expression of the H⁺-ATPases from cells grown under different conditions, showed that the transcript expression of um01205 (plant-type) was higher than that of um02581 (fungal-type). The translation of the two proteins was confirmed by mass spectrometry analysis. Unlike baker's yeast and plant H⁺-ATPases, where the activity is increased by a short incubation with glucose or sucrose, respectively, U. maydis H⁺-ATPase activity did not change in response to these sugars. Sequence analysis of the two U. maydis H⁺-ATPases revealed the lack of canonical threonine and serine residues which are targets of protein kinases in Saccharomyces cerevisiae and Arabidopsis thaliana plasma membrane H⁺-ATPases, suggesting that phosphorylation of the U. maydis enzymes occurs at different amino acid residues.

Metabolic Changes and Antioxidant Response in Ustilago maydis Grown in Acetate.

Ustilago maydis is an important model to study intermediary and mitochondrial metabolism, among other processes. U. maydis can grow, at very different rates, on glucose, lactate, glycerol, and ethanol as carbon sources. Under nitrogen starvation and glucose as the only carbon source, this fungus synthesizes and accumulates neutral lipids in the form of lipid droplets (LD). In this work, we studied the accumulation of triacylglycerols in cells cultured in a medium containing acetate, a direct precursor of the acetyl-CoA required for the synthesis of fatty acids. The metabolic adaptation of cells to acetate was studied by measuring the activities of key enzymes involved in glycolysis, gluconeogenesis, and the pentose phosphate pathways. Since growth on acetate induces oxidative stress, the activities of some antioxidant enzymes were also assayed. The results show that cells grown in acetate plus nitrate did not increase the amount of LD, but increased the activities of glutathione reductase, glutathione peroxidase, catalase, and superoxide dismutase, suggesting a higher production of reactive oxygen species in cells growing in acetate. The phosphofructokinase-1 (PFK1) was the enzyme with the lowest specific activity in the glycolytic pathway, suggesting that PFK1 controls the flux of glycolysis. As expected, the activity of the phosphoenolpyruvate carboxykinase, a gluconeogenic enzyme, was present only in the acetate condition. In summary, in the presence of acetate as the only carbon source, U. maydis synthesized fatty acids, which were directed into the production of phospholipids and neutral lipids for biomass generation, but without any excessive accumulation of LD.

Functional Analysis of the Plasma Membrane H+-ATPases of Ustilago maydis.

Plasma membrane H+-ATPases of fungi, yeasts, and plants act as proton pumps to generate an electrochemical gradient, which is essential for secondary transport and intracellular pH maintenance. Saccharomyces cerevisiae has two genes (PMA1 and PMA2) encoding H+-ATPases. In contrast, plants have a larger number of genes for H+-ATPases. In Ustilago maydis, a biotrophic basidiomycete that infects corn and teosinte, the presence of two H+-ATPase-encoding genes has been described, one with high identity to the fungal enzymes (pma1, UMAG_02851), and the other similar to the plant H+-ATPases (pma2, UMAG_01205). Unlike S. cerevisiae, these two genes are expressed jointly in U. maydis sporidia. In the present work, mutants lacking one of these genes (Δpma1 and Δpma2) were used to characterize the role of each one of these enzymes in U. maydis physiology and to obtain some of their kinetic parameters. To approach this goal, classical biochemical assays were performed. The absence of any of these H+-ATPases did not affect the growth or fungal basal metabolism. Membrane potential tests showed that the activity of a single H+-ATPase was enough to maintain the proton-motive force. Our results indicated that in U. maydis, both H+-ATPases work jointly in the generation of the electrochemical proton gradient, which is important for secondary transport of metabolites and regulation of intracellular pH.

The Mitochondrial Alternative Oxidase in Ustilago maydis Is Not Involved in Response to Oxidative Stress Induced by Paraquat.

It has been shown that the alternative oxidase in mitochondria of fungi and plants has important functions in the response against stress conditions, although their role in some organisms is still unknown. This is the case of Ustilago maydis. There is no evidence of the participation of the U. maydis Aox1 in stressful conditions such as desiccation, high or low temperature, and low pH, among others. Therefore, in this work, we studied the role of the U. maydis Aox1 in cells exposed to oxidative stress induced by methyl viologen (paraquat). To gain insights into the role of this enzyme, we took advantage of four strains: the FB2 wild-type, a strain without the alternative oxidase (FB2aox1Δ), other with the Aox1 fused to the Gfp under the control of the original promoter (FB2aox1-Gfp), and one expressing constitutively de Aox1-Gfp (FB2Potef:aox1-Gfp). Cells were incubated for various times in the presence of 1 mM paraquat and growth, replicative capacities, mitochondrial respiratory activity, Aox1 capacity, and the activities of several antioxidant enzymes (catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase) were assayed. The results show that (1) the response of U. maydis against oxidative stress was the same in the presence or absence of the Aox1; (2) the activities of the antioxidant enzymes remained constant despite the oxidative stress; and (3) there was a decrease in the GSH/GSSG ratio in U. maydis cells incubated with paraquat.

Isolation of Mitochondria from Ustilago maydis Protoplasts.

Ustilago maydis, a basidiomycete that infects Zea mays, is one of the top ten fungal models for studying DNA repair, signal transduction pathways, and dimorphic transitions, among other processes. From a metabolic point of view, U. maydis lacks fermentative capacity, pointing to mitochondria as a key player in central metabolism. Oxidative phosphorylation, synthesis of heme groups, Krebs cycle, ß-oxidation of fatty acids, and synthesis of amino acids are some of the processes that take place in mitochondria. Given the importance of this organelle in eukaryotic cells in general, and in fungal cells in particular, we present a protocol for the isolation of U. maydis mitochondria based on the enzymatic disruption of U. maydis cell wall and differential centrifugation. The method can easily be extrapolated to other fungal species, by using appropriate lytic enzymes.

Response to osmotic stress and temperature of the fungus Ustilago maydis.

Ustilago maydis is a fungal pathogen which is exposed during its life cycle to both abiotic and biotic stresses before and after the infection of maize. To cope with extreme environmental changes, microorganisms usually accumulate the disaccharide trehalose. We have investigated both the accumulation of trehalose and the activity of trehalase during the adaptation of U. maydis haploid cells to thermal, sorbitol, and NaCl stresses. Sorbitol and sodium chloride induced sustained accumulation of trehalose, while a transient increase was observed under heat stress. Sorbitol stressed cells showed higher trehalase activity compared with control cells and to those stressed by NaCl and high temperature. Addition of cycloheximide, a protein synthesis inhibitor, did not affect the trehalose accumulation during the first 15 min, but basal levels of trehalose were reached after the second period of 15 min. The proteomic analysis of the response of U. maydis to temperature, sorbitol, and salt stresses indicated a complex pattern which highlights the change of 18 proteins involved in carbohydrate and amino acid metabolism, protein folding, redox regulation, ion homeostasis, and stress response. We hypothesize that trehalose accumulation during sorbitol stress in U. maydis might be related to the adaptation of this organism during plant infection.

Chitosan resistance by the deletion of the putative high affinity glucose transporter in the yeast Ustilago maydis.

Chitosan is a polycationic amino-sugar polymer soluble in acidic pH. As a potential antifungal, it has been tested against several fungi. Its main mode of action is the permeabilization of cell membrane by the interaction with specific membrane sites. Ustilago maydis, an attractive fungal model used in biochemical and biotechnology research, is highly sensitive to chitosan, with extensive membrane destruction that results in cell death. Using the Golden Gate system, several mutant strains with deletions in monosaccharide transporters were obtained and tested against chitosan in order to know the implications of these membrane proteins in the sensitivity of the fungus against chitosan. Δum11514/03895 strain, a mutant with a deletion in a hypothetical high affinity glucose transporter, showed resistance to chitosan. Morphological characterization of the mutant displayed an apparent increase in mitochondrial content, but oxygen consumption as well as growth rate were not affected by the gene deletion. Alteration in cell wall surface was observed in the mutant strain. In contrast to wild type, the Δum11514/03895 strain showed integrity of cell wall and cell membrane in the presence of chitosan. The resistance against chitosan is likely associated to the modification of cell wall architecture and is not related to energy-depend process.

Carbon and Nitrogen Sources Have No Impact on the Organization and Composition of Ustilago maydis Respiratory Supercomplexes.

Respiratory supercomplexes are found in mitochondria of eukaryotic cells and some bacteria. A hypothetical role of these supercomplexes is electron channeling, which in principle should increase the respiratory chain efficiency and ATP synthesis. In addition to the four classic respiratory complexes and the ATP synthase, U. maydis mitochondria contain three type II NADH dehydrogenases (NADH for reduced nicotinamide adenine dinucleotide) and the alternative oxidase. Changes in the composition of the respiratory supercomplexes due to energy requirements have been reported in certain organisms. In this study, we addressed the organization of the mitochondrial respiratory complexes in U. maydis under diverse energy conditions. Supercomplexes were obtained by solubilization of U. maydis mitochondria with digitonin and separated by blue native polyacrylamide gel electrophoresis (BN-PAGE). The molecular mass of supercomplexes and their probable stoichiometries were 1200 kDa (I1:IV1), 1400 kDa (I1:III2), 1600 kDa (I1:III2:IV1), and 1800 kDa (I1:III2:IV2). Concerning the ATP synthase, approximately half of the protein is present as a dimer and half as a monomer. The distribution of respiratory supercomplexes was the same in all growth conditions. We did not find evidence for the association of complex II and the alternative NADH dehydrogenases with other respiratory complexes.

Lipid Index Determination by Liquid Fluorescence Recovery in the Fungal Pathogen Ustilago Maydis.

The article shows how to implement the LD index assay, which is a sensitive microplate assay to determine the accumulation of triacylglycerols (TAGs) in lipid droplets (LDs). LD index is obtained without lipid extraction. It allows measuring the LDs content in high-throughput experiments under different conditions such as growth in rich or nitrogen depleted media. Albeit the method was described for the first time to study the lipid droplet metabolism in Saccharomyces cerevisiae, it was successfully applied to the basidiomycete Ustilago maydis. Interestingly, and because LDs are organelles phylogenetically conserved in eukaryotic cells, the method can be applied to a large variety of cells, from yeast to mammalian cells. The LD index is based on the liquid fluorescence recovery assay (LFR) of the BODIPY 493/503 under quenching conditions, by the addition of cells fixed with formaldehyde. Potassium iodine is used as a fluorescence quencher. The ratio between the fluorescence and the optical density slopes is named LD index. Slopes are calculated from the straight lines obtained when BODIPY fluorescence and optical density at 600 nm (OD600) are plotted against sample addition. Optimal data quality is reflected by correlation coefficients equal or above 0.9 (r ≥ 0.9). Multiple samples can be read simultaneously as it can be implemented in a microplate. Since BODIPY 493/503 is a lipophilic fluorescent dye that partitions into the lipid droplets, it can be used in many types of cells that accumulate LDs.

Expression of alternative NADH dehydrogenases (NDH-2) in the phytopathogenic fungus Ustilago maydis.

Type 2 alternative NADH dehydrogenases (NDH-2) participate indirectly in the generation of the electrochemical proton gradient by transferring electrons from NADH and NADPH into the ubiquinone pool. Due to their structural simplicity, alternative NADH dehydrogenases have been proposed as useful tools for gene therapy of cells with defects in the respiratory complex I. In this work, we report the presence of three open reading frames, which correspond to NDH-2 genes in the genome of Ustilago maydis. These three genes were constitutively transcribed in cells cultured in YPD and minimal medium with glucose, ethanol, or lactate as carbon sources. Proteomic analysis showed that only two of the three NDH-2 were associated with isolated mitochondria in all culture media. Oxygen consumption by permeabilized cells using NADH or NADPH was different for each condition, opening the possibility of posttranslational regulation. We confirmed the presence of both external and internal NADH dehydrogenases, as well as an external NADPH dehydrogenase insensitive to calcium. Higher oxygen consumption rates were observed during the exponential growth phase, suggesting that the activity of NADH and NADPH dehydrogenases is coupled to the dynamics of cell growth.

Influence of chitosan and its derivatives on cell development and physiology of Ustilago maydis.

Ustilago maydis, a dimorphic fungus causing corn smut disease, serves as an excellent model to study different aspects of cell development. This study shows the influence of chitosan, oligochitosan and glycol chitosan on cell growth and physiology of U. maydis. These biological macromolecules affected the cell growth of U. maydis. In particular, it was found that chitosan completely inhibited U. maydis growth at 1mg/mL concentration. Microscopic studies revealed swellings on the surface of the cells treated with the polymers, and chitosan caused complete destruction of the membrane and formation of vesicles on the periphery of the cell. Oligochitosan and chitosan caused changes in oxygen consumption, K(+) efflux and H(+)-ATPase activity. Oligochitosan induced a faster consumption of oxygen in the cells, while glycol chitosan provoked slower oxygen consumption. It is noteworthy that chitosan completely inhibited the fungal respiratory activity. The strongest effects were exhibited by chitosan in all evaluated aspects. These findings showed high sensitivity of U. maydis to chitosan and provided evidence for antifungal effects of chitosan derivatives. To our knowledge, this is a first report showing that chitosan and its derivatives affect the cell morphology and physiological processes in U. maydis.

Las funciones metabólicas, endocrinas y reguladoras de la expresión genética del lactato / The metabolic, endocrine and regulatory functions of lactate gene expression

Resumen El lactato se considera un metabolito de desecho que se produce durante la fatiga muscular. En contraste con esta visión simplista, en este trabajo se proporcionan evidencias de las múltiples y complejas funciones de este metabolito. Se muestra que: 1) el lactato es el producto final de la glucólisis, independientemente de la concentración de oxígeno en el medio en el que se encuentren las células; 2) el lactato forma parte de 2 tipos de lanzadera, una que funciona en el espacio intermembranal de la mitocondria, y otra intercelular, que se encarga de alimentar con lactato a ciertos tipos celulares, como las neuronas o el músculo cardiaco; 3) en los espermatozoides, el lactato se transporta directamente a la matriz mitocondrial y allí se oxida para producir piruvato y NADH; 4) en el hígado, el lactato participa en la oxidación del etanol a través de la generación de peróxido de hidrógeno; 5) que dependiendo de la estirpe celular, el lactato puede funcionar como agente antiinflamatorio (endocrino) o regulador de la expresión génica.

Abstract Lactate is considered to be a waste metabolite produced during muscle fatigue. In contrast with this simplistic point of view, in this review we provide evidence of the multiple and complex functions of this metabolite. We show that: 1) lactate is the final product of the glycolysis regardless the oxygen concentration in the cell 2) lactate is part of two types of shuttle, one that functions in the intermembrane space of the mitochondrion, and another intercellular, which is responsible for feeding lactate to certain cell types, such as neurons or heart muscle, 3) in sperm, lactate is transported directly to the mitochondrial matrix and there it is oxidized to produce pyruvate and NADH, 4) in the liver, lactate participates in the oxidation of ethanol through the generation of hydrogen peroxide, 5) Depending on the cell line, lactate can function as anti-inflammatory agent (endocrine) and/or a regulator of gene expression.