The CAZy auxiliary activity family 3 (AA3) comprises FAD-dependent enzymes belonging to the superfamily of glucose-methanol-choline (GMC) oxidoreductases. Glucose oxidase (GOx; EC 1.1.3.4) and glucose dehydrogenase (GDH; EC 1.1.5.9) are part of subfamily AA3_2 and catalyze the oxidation of β-D-glucose at its anomeric carbon to D-glucono-1,5-lactone. Recent phylogenetic analysis showed that AA3_2 glucose oxidoreductases can be grouped into four major clades, GOx I and GDH I–III, and in minor clades such as GOx II or distinct subclades. This wide sequence space of AA3_2 glucose oxidoreductases has, however, not been studied in detail, with mainly members of GOx I and GDH I studied biochemically or structurally. Here, we report the biochemical characterization of four fungal glucose oxidoreductases from distinct, hitherto unexplored clades or subclades. The enzyme from Aureobasidium subglaciale, belonging to the minor GOx II clade, showed a typical preference for oxygen and glucose, confirming the correct annotation of this clade. The other three enzymes exhibited strict dehydrogenase activity with different substrate specificities. GDH II from Trichoderma virens showed an almost six-fold higher catalytic efficiency for maltose compared to glucose. The preferred substrate for the two GDH III enzymes from Rhizoctonia solani and Ustilago maydis was gentiobiose, a β(1→6) disaccharide, as judged from the catalytic efficiency. Overall, the newly studied AA3_2 glucose oxidoreductases showed a much broader substrate spectrum than the archetypal GOx from Aspergillus niger, which belongs to clade GOx I.

Chicken cartilage (claw) is a waste of chicken cuts which are widely available in Indonesia. Cartilage part of chicken claw becomes a potential source of chondroitin sulfate (CS) and glucosamine (GS). This aim of this study was to determine the most optimal extraction methods of CS and GS from cartilage of chicken claw. Various types of extraction methods used in this study were taken from the extraction by using boiling water (2 and 2.5 hours), acetic acid (7 and 17 hours), as well as proteolysis by papain (24 and 48 hours). Parameters observed include chemical characteristics of powdered cartilage of chicken claw as well as CS and GS levels in powdered cartilage of chicken claw extract. The results showed that the levels of CS and GS of chicken claw cartilage powder were 2.17% and 13%, respectively. The highest GS level was obtained from the extraction with water treatment for 2.5 hours (8.1%). The treatment and duration of extraction will significantly affect the number of GS which was produced. The highest content of CS was obtained from the extraction with the enzyme treatment for 48 hours (2.47%). The best treatment is the extraction with water treatment for 2.5 hours which were the extracts with GS levels of 8.1% and 2.03% CS was selected through the analysis of multiple attribute.

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