[Identification of a new C-23 metabolite in sterol degradation of Mycobacterium neoaurum HGMS2 and analysis of its metabolic pathways].

Mycobacterium neoaurum has the ability to produce steroidal intermediates known as 22-hydroxy-23, 24-bisnorchol-4-en-3-one (BA) upon the knockout of the genes for either the hydroxyacyl-CoA dehydrogenase (Hsd4A) or acyl-CoA thiolase (FadA5). In a previous study, we discovered a novel metabolite in the fermentation products when the fadA5 gene was deleted. This research aims to elucidate the metabolic pathway of this metabolite through structural identification, homologous sequence analysis of the fadA5 gene, phylogenetic tree analysis of M. neoaurum HGMS2, and gene knockout. Our findings revealed that the metabolite is a C23 metabolic intermediate, named 24-norchol-4-ene-3, 22-dione (designated as 3-OPD). It is formed when a thioesterase (TE) catalyzes the formation of a ß-ketonic acid by removing CoA from the side chain of 3, 22-dioxo-25, 26-bisnorchol-4-ene-24-oyl CoA (22-O-BNC-CoA), followed by spontaneously undergoing decarboxylation. These results have the potential to contribute to the development of novel steroid intermediates.

Production and evaluation of enzyme-modified cheese adding protease or lipase to improve quality properties.

Enzyme-modified cheese (EMC) produced by enzyme hydrolysis is a natural, cost-effective, and flexible alternative to using natural cheese in industrial applications. The modification of cheese by enzymes can increase their benefits for consumer acceptance and health, and intensify the specific cheese flavor. We evaluated the properties of cheese with added protease (Ep) or lipase (El), including texture, sensory, organic acids, volatile compounds, and free amino acids. As results, the hardness and gumminess of the cheese reached their maximum values when the concentration of protease and lipase was 0.1% and 0.6%, respectively. Interestingly, the bitterness and astringency of the cheese was reduced. The highest scores for odor, taste, and overall acceptability were observed on 0.08% protease in Ep and 0.8% lipase in El. Compared with the anchor cheese, eight new compounds were produced after the addition of protease and nine new compounds were produced after the addition of lipase. Irrespective of the type of enzyme, the content of free amino acids decreased slightly with the increase in enzyme content. From the point of view of adding enzyme species, the free amino acids content of Ep was generally higher than that of El, and glutamic acid and proline contents were high. Acetic acid concentrations (aroma-active compounds) of enzyme-modified cheese using protease and lipase were 482-931 mg/100 g and 30-36 mg/100 g, respectively, which were significantly increased. According to the results obtained in this study, a cheese with higher sensorial and textural acceptability was obtained by adding the appropriate protease or lipase.

The transcription factor PbrbZIP52 positively affects pear pollen tube longevity by promoting callose synthesis.

In pear (Pyrus bretschneideri), pollen tube growth is critical for the double fertilization associated with seed setting, which in turn affects fruit yield. The normal deposition of callose mediates the polar growth of pollen tubes. However, the mechanism regulating callose synthesis in pollen tubes remains relatively uncharacterized. In this study, we revealed that the typical pear pollen tube lifecycle has a semi-growth duration (GD50) of 16.16 h under in vitro culture conditions. Moreover, callose plugs were deposited throughout the pollen tube lifecycle. The formation of callose plugs was inhibited by 2-deoxy-D-glucose, which also accelerated the senescence of pear pollen tubes. Additionally, PbrCalS1B.1, which encodes a plasma membrane-localized callose synthase, was expressed specifically in pollen tubes and restored the fertility of the Arabidopsis (Arabidopsis thaliana) cals5 mutant, in which callose synthesis is inhibited. However, this restoration of fertility was impaired by the transient silencing of PbrCalS1B.1, which restricts callose plug formation and shortens the pear pollen tube lifecycle. More specifically, PbrbZIP52 regulated PbrCalS1B.1 transcription by binding to promoter A-box elements to maintain the periodic formation of callose plugs and normal pollen tube growth, ultimately leading to double fertilization. This study confirmed that PbrbZIP52 positively affects pear pollen tube longevity by promoting callose synthesis. This finding may be useful for breeding high-yielding pear cultivars and stabilizing fruit setting in commercial orchards.