Juniperus communis extract induces cell cycle arrest and apoptosis of colorectal adenocarcinoma in vitro and in vivo.

Juniperus communis (JCo) is a well-known traditional Chinese medicinal plant that has been used to treat wounds, fever, swelling, and rheumatism. However, the mechanism underlying the anticancer effect of JCo extract on colorectal cancer (CRC) has not yet been elucidated. This study investigated the anticancer effects of JCo extract in vitro and in vivo as well as the precise molecular mechanisms. Cell viability was evaluated using the MTT assay. Cell cycle distribution was examined by flow cytometry analysis, and cell apoptosis was determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Protein expression was analyzed using western blotting. The in vivo activity of the JCo extract was evaluated using a xenograft BALB/c mouse model. The tumors and organs were examined through hematoxylin-eosin (HE) staining and immunohistochemistry. The results showed that JCo extract exhibited higher cytotoxicity against CRC cells than against normal cells and showed synergistic effects when combined with 5-fluorouracil. JCo extract induced cell cycle arrest at the G0/G1 phase via regulation of p53/p21 and CDK4/cyclin D1 and induced cell apoptosis via the extrinsic (FasL/Fas/caspase-8) and intrinsic (Bax/Bcl-2/caspase-9) apoptotic pathways. In vivo studies revealed that JCo extract suppressed tumor growth through the inhibition of proliferation and induction of apoptosis. In addition, there was no obvious change in body weight or histological morphology of normal organs after treatment. JCo extract suppressed CRC progression by inducing cell cycle arrest and apoptosis in vitro and in vivo, suggesting the potential application of JCo extract in the treatment of CRC.

Pogostemon cablin extract as an anticancer agent on human acute myeloid leukemia.

Pogostemon cablin has been indicated to treat many kinds of diseases and the progression of cancers, such as colorectal cancer. However, the effects of P. cablin extract (PPa extract) against acute myeloid leukemia have not been investigated. Thus, this study explored the anticancer potential of PPa extract and its mechanism in HL-60 cells. The MTT assay results showed that PPa extract significantly inhibited the proliferation of HL-60 cells in a dose-dependent manner and affected cell morphology, causing cell shrinkage and the formation of debris. PPa extract blocked cell cycle progression at the G0/G1 phase in a dose- and time-dependent manner and induced cell apoptosis, as shown by the observation of DNA fragments and apoptotic bodies. Furthermore, PPa extract caused the accumulation of a population of cells at G0/G1 phase via a reduction in p-Rb, increasing p21 expression, and downregulating cell cycle regulator protein expression. Then, PPa extract was found to activate the extrinsic and intrinsic apoptosis pathways, leading to cell death. These data demonstrated that PPa extract exerted inhibitory activity and triggered cell apoptosis in HL-60 cells and that PPa extract might be a chemopreventive agent for cancer therapy.

Cell cycle arrest and apoptosis induction by Juniperus communis extract in esophageal squamous cell carcinoma through activation of p53-induced apoptosis pathway.

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers. It has a high mortality rate and requires novel effective drugs and therapeutic approaches. Juniperus communis (JCo), used to flavor gin and food, has been documented to have anti-tumor activity. The aim of this study was to investigate the antitumor activity of JCo extract against ESCC and its possible mechanisms. JCo extract suppressed cell growth in ESCC and showed higher selection for ESCC cells than normal cells compared to the clinical drug 5-fluorouracil (5-FU). JCo extract induced cell cycle arrest at the G0/G1 phase by regulating the expression of p53/p21 and CDKs/cyclins, triggering cell apoptosis by activating both the extrinsic (Fas/FasL/Caspase 8) and intrinsic (Bcl-2/Bax/Caspase 9) apoptosis pathways. Moreover, a combination treatment of JCo and 5-FU synergistically inhibited proliferation of ESCC cells. These results suggest that JCo extract is a potential natural therapeutic agent for esophageal cancer, as it could induce cell cycle arrest and apoptosis in ESCC cells.

Juniperus communis extract induces cell cycle arrest and apoptosis of colorectal adenocarcinoma in vitro and in vivo

Juniperus communis (JCo) is a well-known traditional Chinese medicinal plant that has been used to treat wounds, fever, swelling, and rheumatism. However, the mechanism underlying the anticancer effect of JCo extract on colorectal cancer (CRC) has not yet been elucidated. This study investigated the anticancer effects of JCo extract in vitro and in vivo as well as the precise molecular mechanisms. Cell viability was evaluated using the MTT assay. Cell cycle distribution was examined by flow cytometry analysis, and cell apoptosis was determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Protein expression was analyzed using western blotting. The in vivo activity of the JCo extract was evaluated using a xenograft BALB/c mouse model. The tumors and organs were examined through hematoxylin-eosin (HE) staining and immunohistochemistry. The results showed that JCo extract exhibited higher cytotoxicity against CRC cells than against normal cells and showed synergistic effects when combined with 5-fluorouracil. JCo extract induced cell cycle arrest at the G0/G1 phase via regulation of p53/p21 and CDK4/cyclin D1 and induced cell apoptosis via the extrinsic (FasL/Fas/caspase-8) and intrinsic (Bax/Bcl-2/caspase-9) apoptotic pathways. In vivo studies revealed that JCo extract suppressed tumor growth through the inhibition of proliferation and induction of apoptosis. In addition, there was no obvious change in body weight or histological morphology of normal organs after treatment. JCo extract suppressed CRC progression by inducing cell cycle arrest and apoptosis in vitro and in vivo, suggesting the potential application of JCo extract in the treatment of CRC.

From fragmentation toward integration: a preliminary study of a new long-term care policy in a fast-aging country.

BACKGROUND: Taiwan, one of the fastest-aging countries in the world, started implementing version 1.0 of its long-term care (LTC) plan in 2008. In 2017, LTC Plan 2.0 began a new era with its goal to integrate Taiwan's fragmented LTC service system. LTC Plan 2.0 also aims to establish an integrated community-based LTC system incorporating both health care and disability prevention. This three-tier model consists of the following: two LTC services with a day-care center as their base and case management (Tier A), a day-care center and a single LTC service (Tier B), and LTC stations that provide primary prevention services and respite services for frail community-dwelling older adults to prevent further disabilities (Tier C). A defined cluster of agencies in a local area works together as a Tier ABC team. LTC Plan 2.0 is a new policy for Taiwan, and hence it is important to understand the agencies' initial difficulties with implementation and identify future challenges to help further policy development. METHODS: This preliminary study explored the challenges to implementing LTC 2.0 through in-depth interviews based on Evashwick's integration mechanisms with representatives from three service teams. We interviewed three chief executive officers and three case managers. RESULTS: We found that the LTC Plan 2.0 mechanisms for service integration have been insufficiently implemented. Recommendations include (1) Build up the trust between agencies and government, avoid duplication of LTC services within Tier ABC team, and encourage agencies within a team to create a shared administrative system with the same mission and vision. (2) Clarify the roles and responsibilities of government care managers and agency case managers. (3) Provide an integrated information system and create an official platform for sharing client records across different agencies and caregivers. (4) Establish a tool and platform to track the budget and payment across different levels of service as soon as possible. CONCLUSION: There is an increased demand for LTC services in Taiwan because of its rapidly aging population. Our findings shed some light on the challenges to developing integrated LTC services and thus may help both policymakers and service providers find ways to overcome these challenges.

Effect of Lactobacillus plantarum Strain K21 on High-Fat Diet-Fed Obese Mice.

Recent studies have demonstrated beneficial effects of specific probiotics on alleviating obesity-related disorders. Here we aimed to identify probiotics with potential antiobesity activity among 88 lactic acid bacterial strains via in vitro screening assays, and a Lactobacillus plantarum strain K21 was found to harbor abilities required for hydrolyzing bile salt, reducing cholesterol, and inhibiting the accumulation of lipid in 3T3-L1 preadipocytes. Furthermore, effects of K21 on diet-induced obese (DIO) mice were examined. Male C57Bl/6J mice received a normal diet, high-fat diet (HFD), or HFD with K21 administration (10(9) CFU in 0.2 mL PBS/day) for eight weeks. Supplementation of K21, but not placebo, appeared to alleviate body weight gain and epididymal fat mass accumulation, reduce plasma leptin levels, decrease cholesterol and triglyceride levels, and mitigate liver damage in DIO mice. Moreover, the hepatic expression of peroxisome proliferator-activated receptor-γ (PPAR-γ) related to adipogenesis was significantly downregulated in DIO mice by K21 intervention. We also found that K21 supplementation strengthens intestinal permeability and modulates the amount of Lactobacillus spp., Bifidobacterium spp., and Clostridium perfringens in the cecal contents of DIO mice. In conclusion, our results suggest that dietary intake of K21 protects against the onset of HFD-induced obesity through multiple mechanisms of action.

The Methanol Extract of Angelica sinensis Induces Cell Apoptosis and Suppresses Tumor Growth in Human Malignant Brain Tumors.

Glioblastoma multiforme (GBM) is a highly vascularized and invasive neoplasm. The methanol extract of Angelica sinensis (AS-M) is commonly used in traditional Chinese medicine to treat several diseases, such as gastric mucosal damage, hepatic injury, menopausal symptoms, and chronic glomerulonephritis. AS-M also displays potency in suppressing the growth of malignant brain tumor cells. The growth suppression of malignant brain tumor cells by AS-M results from cell cycle arrest and apoptosis. AS-M upregulates expression of cyclin kinase inhibitors, including p16, to decrease the phosphorylation of Rb proteins, resulting in arrest at the G0-G1 phase. The expression of the p53 protein is increased by AS-M and correlates with activation of apoptosis-associated proteins. Therefore, the apoptosis of cancer cells induced by AS-M may be triggered through the p53 pathway. In in vivo studies, AS-M not only suppresses the growth of human malignant brain tumors but also significantly prolongs patient survival. In addition, AS-M has potent anticancer effects involving cell cycle arrest, apoptosis, and antiangiogenesis. The in vitro and in vivo anticancer effects of AS-M indicate that this extract warrants further investigation and potential development as a new antibrain tumor agent, providing new hope for the chemotherapy of malignant brain cancer.

Evolution of vitamin B2 biosynthesis: eubacterial RibG and fungal Rib2 deaminases.

Eubacterial RibG and yeast Rib2 possess a deaminase domain for pyrimidine deamination in the second and third steps, respectively, of riboflavin biosynthesis. These enzymes are specific for ribose and ribitol, respectively. Here, the crystal structure of Bacillus subtilis RibG in complex with a deaminase product is reported at 2.56 Å resolution. Two loops move towards the product on substrate binding, resulting in interactions with the ribosyl and phosphate groups and significant conformational changes. The product carbonyl moiety is bent out of the pyrimidine ring to coordinate to the catalytic zinc ion. Such distortions in the bound substrate and product may play an essential role in enzyme catalysis. The yeast Rib2 structure was modelled and a mutational analysis was carried out in order to understand the mechanism of substrate recognition in these two enzymes. Detailed structural comparisons revealed that the two consecutive carbonyl backbones that occur prior to the PCXXC signature constitute a binding hole for the target amino group of the substrate. This amino-binding hole is essential in B. subtilis RibG and is also conserved in the RNA/DNA-editing deaminases.

Analysis of bacterial diversity during the fermentation of inyu, a high-temperature fermented soy sauce, using nested PCR-denaturing gradient gel electrophoresis and the plate count method.

The diversity of bacteria associated with the fermentation of inyu, also known as black soy sauce, was studied through the nested PCR-denaturing gradient gel electrophoresis (DGGE) of samples collected from the fermentation stages of the inyu production process. The DGGE profiles targeted the bacterial 16S rDNA and revealed the presence of Citrobacter farmeri, Enterobacter cloacae, Enterobacter hormaechei, Enterococcus faecium, Klebsiella pneumoniae, Pantoea agglomerans, Salmonella enterica, Serratia marcescens, Staphylococcus sciuri and Weissella confusa. The bacterial compositions of 4 fermented samples were further elucidated using the plate count method. The bacteria isolated from the koji-making stage exhibited the highest diversity; Brachybacterium rhamnosum, E. hormaechei, K. pneumoniae, Kurthia gibsonii, Pantoea dispersa, Staphylococcus gallinarum, Staphylococcus kloosii and S. sciuri were identified. Koji collected during the preincubation stage presented the largest cell counts, and E. hormaechei, K. pneumoniae, E. cloacae and Enterobacter pulveris were identified. In brine samples aged for 7 and 31 days, the majority of the bacteria isolated belonged to 4 Bacillus species, but 4 Staphylococcus species and Delftia tsuruhatensis were also detected. This study demonstrates the benefits of using a combined approach to obtain a more complete picture of microbial populations and provides useful information for the control or development of bacterial flora during inyu fermentation.

The inhibitory activity of linalool against the filamentous growth and biofilm formation in Candida albicans.

Candida spp. are part of the natural human microbiota, but they also represent important opportunistic human pathogens. Biofilm-associated Candida albicans infections are clinically relevant due to their high levels of resistance to traditional antifungal agents. In this study, we investigated the ability of linalool to inhibit the formation of C. albicans biofilms and reduce existing C. albicans biofilms. Linalool exhibited antifungal activity against C. albicans ATCC 14053, with a minimum inhibitory concentration (MIC) of 8 mM. Sub-MIC concentrations of linalool also inhibited the formation of germ tubes and biofilms in that strain. The defective architecture composition of C. albicans biofilms exposed to linalool was characterized by scanning electron microscopy. The expression levels of the adhesin genes HWP1 and ALS3 were downregulated by linalool, as assessed by real-time RT-PCR. The expression levels of CYR1 and CPH1, which encode components of the cAMP-PKA and MAPK hyphal formation regulatory pathways, respectively, were also suppressed by linalool, as was the gene encoding their upstream regulator, Ras1. The expression levels of long-term hyphae maintenance associated genes, including UME6, HGC1, and EED1, were all suppressed by linalool. These results indicate that linalool may have therapeutic potential in the treatment of candidiasis associated with medical devices because it interferes with the morphological switch and biofilm formation of C. albicans.

Inhibition of herpes simplex virus type 1 by thymol-related monoterpenoids.

This study examined the anti-herpes simplex virus type I activity of the major constituents of several essential oils. Plaque reduction assays were performed to evaluate anti-herpes simplex virus type I activity. Thymol and carvacrol both possessed significant antiviral activity with an IC50 of 7 µM, and herpes simplex virus type I was 90 % inactivated within 1 hr. The mode of antiviral action was shown to affect the virion directly. Evidence was also observed by electron microscopy. Evaluation of the structural requirements for antiviral activity of thymol-related monoterpenoids revealed that aliphatic side chains had a minor effect, while a hydrophilic group on the benzene ring was sufficient for activity. Our results suggest that thymol and carvacrol are potential candidates for topical therapeutic application to reduce herpes simplex virus transmission.

Mechanisms of Panax ginseng in preventing rat pheochromocytoma cells from apoptosis.

AIMS OF THE STUDY: Although ginseng root possesses dominant central therapeutic effects and has recently undergone investigations for treating different neuronal diseases, most of its mechanisms are still unknown. Therefore, the neuroprotective mechanisms of ginseng were studied. MATERIALS AND METHODS: The protection afforded by different methanol extracts of Panax ginseng (PG) was tested in a serum deprivation-induced apoptotic model using neuronal-like pheochromocytoma (PC12) cells. An MTT assay, annexin V-FITC staining, and Western blots were, respectively, applied to identify the viability of cells, the apoptotic form of cell death, and the activity of antiapoptotic signaling. RESULTS: The known antiapoptotic PI3-K/Akt and MEK/ERK pathways in this system were ruled out due to failure of LY 294002 and PD 98059 to block the protection by PG. A protein kinase A (PKA) inhibitor was found to block the protection by PG and PG-induced CREB phosphorylation, suggesting that the PKA/CREB pathway mediates the protective effect of PG. Downregulation of classical and novel PKCs failed to block the protection by PG, while an atypical PKC inhibitor blocked protection by PG. CONCLUSIONS: PKA and atypical PKC are important for the protection afforded by PG in preventing serum deprivation-induced PC12 cell apoptosis.

Ligusticum chuanxiong as a potential neuroprotectant for preventing serum deprivation-induced apoptosis in rat pheochromocytoma cells: functional roles of mitogen-activated protein kinases.

ETHNOPHARMACOLOGICAL RELEVANCE: Ligusticum chuanxiong (LC) as a common component in many traditional Chinese medicinal formulas and decoctions has been used to treat different central nervous diseases, suggesting a neuroprotective function. AIM OF THE STUDY: To investigate the functional roles of mitogen-activated protein kinases (MAPKs) in mediating the neuroprotection of LC. MATERIALS AND METHODS: Different extractions of LC were applied with or without MAPK inhibitor to test their protection against serum deprivation-induced apoptosis in rat neuronal-like pheochromocytoma (PC12) cells as revealed by an MTT assay or Hoechst staining. Western blot was used to identify the activations of MAPKs. RESULTS: The most effective butanol extraction (LC-BuOH) was used in the following experiments. LC-BuOH reversed serum deprivation-induced decreased phosphorylation of extracellular signal-regulated kinase (ERK) and increased phosphorylation of c-Jun NH(2)-terminal kinase (JNK) and p38, the family of MAPKs. A PKA inhibitor, blocked the protection of LC-BuOH and partially blocked LC-BuOH-induced alterations in MAPKs, suggesting that the LC-BuOH regulates MAPKs through both PKA-dependent and -independent pathways. Although PD 98059, an inhibitor of MEK which activates ERK, blocked LC-BuOH-induced ERK phosphorylation, it did not block the protection of LC-BuOH. CONCLUSIONS: LC-BuOH mediates protection by suppressing JNK/p38 instead of activating ERK activity.

Functional roles of the 6-S-cysteinyl, 8alpha-N1-histidyl FAD in glucooligosaccharide oxidase from Acremonium strictum.

The crystal structure of glucooligosaccharide oxidase from Acremonium strictum was demonstrated to contain a bicovalent flavinylation, with the 6- and 8alpha-positions of the flavin isoalloxazine ring cross-linked to Cys(130) and His(70), respectively. The H70A and C130A single mutants still retain the covalent FAD, indicating that flavinylation at these two residues is independent. Both mutants exhibit a decreased midpoint potential of approximately +69 and +61 mV, respectively, compared with +126 mV for the wild type, and possess lower activities with k(cat) values reduced to approximately 2 and 5%, and the flavin reduction rate reduced to 0.6 and 14%. This indicates that both covalent linkages increase the flavin redox potential and alter the redox properties to promote catalytic efficiency. In addition, the isolated H70A/C130A double mutant does not contain FAD, and addition of exogenous FAD was not able to restore any detectable activity. This demonstrates that the covalent attachment is essential for the binding of the oxidized cofactor. Furthermore, the crystal structure of the C130A mutant displays conformational changes in several cofactor and substrate-interacting residues and hence provides direct evidence for novel functions of flavinylation in assistance of cofactor and substrate binding. Finally, the wild-type enzyme is more heat and guanidine HCl-resistant than the mutants. Therefore, the bicovalent flavin linkage not only tunes the redox potential and contributes to cofactor and substrate binding but also increases structural stability.

Fermented Antrodia cinnamomea extract protects rat PC12 cells from serum deprivation-induced apoptosis: the role of the MAPK family.

Antrodia cinnamomea (formerly A. camphorata) has recently and commercially been used in the formulation of nutraceuticals and functional foods in Taiwan. Because of its diverse properties, the neuroprotective effect was investigated using a fermented A. cinnamomea extract in this study. Serum deprivation-induced apoptosis in neuronal-like pheochromocytoma (PC12) cells was used as a cell stress model, and it was found that A. cinnamomea was effective in preventing serum-deprived apoptosis according to results of an MTT assay and Hoechst staining. Serum deprivation resulted in decreased phosphorylation of extracellular signal-regulated kinase (ERK) and increased phosphorylations of c-Jun NH2-terminal kinase (JNK) and p38, of the family of mitogen-activated protein kinases (MAPKs); however, A. cinnamomea reversed these phenomena, supporting the antagonistic effects between ERK and JNK-p38 in regulating cell survival. The previously identified active component of A. cinnamomea, adenosine (ADO), also exerted the same effects as A. cinnamomea in preventing apoptosis and regulating phosphorylations of MAPKs. Although an inhibitor of the ERK upstream activator blocked A. cinnamomea-induced ERK phosphorylations, it failed to block the protection of A. cinnamomea and ADO. A protein kinase A (PKA) inhibitor blocked the protection by both A. cinnamomea and ADO. Both JNK and p38 inhibitors were effective in preventing the phosphorylations of JNK and p38 and serum deprivation-induced apoptosis. Collectively, A. cinnamomea prevented serum deprivation-induced PC12 cell apoptosis through a PKA-dependent pathway and by suppression of JNK and p38 activities.

Methamphetamine downregulates peroxiredoxins in rat pheochromocytoma cells.

Methamphetamine (METH) is an abusive psychostimulant that induces neuronal cell death/degeneration in experimental animals and humans. METH-induced apoptosis in rat pheochromocytoma cells was utilized to study the neurotoxic mechanism. During METH intoxication, we found that peroxiredoxins and thioredoxins/thioredoxin reductases (peroxiredoxin reducing systems) which are known to prevent oxidative stress and apoptosis were differentially downregulated and upregulated, respectively. We also found not only the free radicals but also the oxidative forms of peroxiredoxin and thioredoxin were increased, indicating the dysfunction of these enzymes. Thus, METH-induced differential regulation and oxidation of peroxiredoxins and thioredoxin may be an important mechanism for apoptosis.

Ligusticum chuanxiong prevents rat pheochromocytoma cells from serum deprivation-induced apoptosis through a protein kinase A-dependent pathway.

Ligusticum chuanxiong (LC) is a traditional Chinese herbal medicine used to treat various cardiovascular diseases. In this study, the butanol extract of LC was found to protect neuronal-like pheochromocytoma cells from serum deprivation-induced apoptosis. Both a serine/threonine kinase inhibitor and a specific protein kinase A (PKA) inhibitor blocked the protective effect of LC. A transcription inhibitor (actinomycin D) and a protein synthesis inhibitor (cyclohexamide) also attenuated the protective effect of LC, suggesting the requirement of gene expression for the protection of LC. On the other hand, LC increased both the formation of cyclic-AMP and the phosphorylation of the cyclic-AMP response element-binding protein (CREB), a downstream target of PKA and a nuclear transcription factor known for neuroprotective mechanism. Furthermore, LC-induced CREB phosphorylation and protective effect could be blocked by a PKA inhibitor and overexpression of the dominant negative CREB, respectively. Taken together, the protective mechanism of LC in antagonizing serum deprivation-induced PC12 cell apoptosis might be mediated through a PKA/CREB-dependent pathway.

Adenosine as an active component of Antrodia cinnamomea that prevents rat PC12 cells from serum deprivation-induced apoptosis through the activation of adenosine A(2A) receptors.

Antrodia cinnamomea (formerly named Antrodia camphorata) is a rare medicinal fungus. We previously reported that it exhibits antioxidative, vasorelaxative, anti-inflammatory, and anti-angiogenic effects. When serum deprivation-induced apoptosis in neuronal-like PC12 cells was used as a stress model, the extract of A. cinnamomea displayed effectiveness in preventing serum-deprived apoptosis. Since our previous data show that the extract of A. cinnamomea contains adenosine (ADO), we attempt to investigate if the active component is ADO and to identify its targeting site in this study. After pre-incubation with ADO deaminase, neither ADO nor the extract of A. cinnamomea exerted any protection, demonstrating that the active component of A. cinnamomea is ADO. Furthermore, an ADO A(2A) receptor (A(2A)-R) antagonist was used and was able to block the protective effects of ADO and the extract of A. cinnamomea, demonstrating that the ADO targeting site in this model is A(2A)-R. Taken together, the protective effect of A. cinnamomea is owed to its active component, ADO, which acts through activation of A(2A)-R to prevent serum deprivation-induced PC12 cell apoptosis.

Structural characterization of glucooligosaccharide oxidase from Acremonium strictum.

Glucooligosaccharide oxidase from Acremonium strictum was screened for potential applications in oligosaccharide acid production and carbohydrate detection. This protein is a unique covalent flavoenzyme which catalyzes the oxidation of a variety of carbohydrates with high selectivity for cello- and maltooligosaccharides. Kinetic measurements suggested that this enzyme possesses an open carbohydrate-binding groove, which is mainly composed of two glucosyl-binding subsites. The encoding gene was subsequently cloned, and one intron was detected in the genomic DNA. Large amounts of active enzymes were expressed in Pichia pastoris, with a yield of 300 mg per liter medium. The protein was predicted to share structural homology with plant cytokinin dehydrogenase and related flavoproteins that share a conserved flavin adenine dinucleotide (FAD)-binding domain. The closest sequence matches are those of plant berberine bridge enzyme-like proteins, particularly the characteristic flavinylation site. Unexpectedly, mutation of the putative FAD-attaching residue, H70, to alanine, serine, cysteine, and tyrosine did not abolish the covalent FAD linkage and had little effect on the Km. Instead, the variants displayed kcat values that were 50- to 600-fold lower, indicating that H70 is crucial for efficient redox catalysis, perhaps through modulation of the oxidative power of the flavin.

Crystal structure of glucooligosaccharide oxidase from Acremonium strictum: a novel flavinylation of 6-S-cysteinyl, 8alpha-N1-histidyl FAD.

Glucooligosaccharide oxidase from Acremonium strictum has been screened for potential applications in oligosaccharide acid production and alternative carbohydrate detection, because it catalyzes the oxidation of glucose, maltose, lactose, cellobiose and cello- and maltooligosaccharides. We report the crystal structures of the enzyme and of its complex with an inhibitor, 5-amino-5-deoxy- cellobiono-1,5-lactam at 1.55- and 1.98-A resolution, respectively. Unexpectedly, the protein structure demonstrates the first known double attachment flavinylation, 6-S-cysteinyl, 8alpha-N1-histidyl FAD. The FAD cofactor is cross-linked to the enzyme via the C(6) atom and the 8alpha-methyl group of the isoalloxazine ring with Cys(130) and His(70), respectively. This sugar oxidase possesses an open carbohydrate-binding groove, allowing the accommodation of higher oligosaccharides. The complex structure suggests that this enzyme may prefer a beta-d-glucosyl residue at the reducing end with the conserved Tyr(429) acting as a general base to abstract the OH(1) proton in concert with the H(1) hydride transfer to the flavin N(5). Finally, a detailed comparison illustrates the structural conservation as well as the divergence between this protein and its related flavoenzymes.