L-serine dehydratase in some filamentous fungi I Studies on the formation of L-serine dehydratase by cunninghamella elegans and fusarium oxysporum

Cunninghamella elegans and Fusarium oxysporum were selected as the most potent producers of L-serine dehydratase among 16 different fungi. Of the tested metal salts, FeSO4 was the best inducer for L- serine dehydratase synthesis by C. Elegans and F. oxysporum. The enzyme was produced during the logarithmic phase of growth of the two organisms and maximum production was obtained after 3 days incubation. The optimal pH range for L-serine dehydratase formation in F. oxysporum was 4-5, whereas for C. Elegans enzyme pH 5.0 was the optimal. L-serine dehydratase of both organisms was induced with L- serine, ammonium carbonate, some amino acids and amides, but L-serine was the best induced. L-serine concentration of 2.4 gm/I was the optimal for L-serine dehydratase synthesis by both cultures. The effect of different carbon sources on enzyme formation and growth of the two organisms was investigated

L-Serine dehydratase in some filamentous fungi II- comparative properties of L-Serine dehydratase of cunninghamella elegans and fusarium oxysporum

L-Serine dehydratase [EC 4.21.13] of Cunninghamella elegans and Fusarium oxysporum had a pH optimum of 8. Maximal activity of L- serine dehydratase of C. elegans occurred at 50C, while that of F. oxysporum enzyme was optimal at 40-50C. Both enzymes were thermolabile Km of C. elegans enzyme for L-Serine was 20 mM, whereas that of F. Oxysporum enzyme was 30 mM. The two enzymes were highly specific for L-Serine. The catalytic activity of both enzymes was inhibited by Zn2+, Cu2, Co2+, Mn2+ and Ca2+. No cofactor requirement was observed for both enzymes. L-Cysteine inhibited C. elegans enzyme competitively with a Ki of 0.87 mM and that of F. Oxysporum enzyme noncompetitively with a Ki of 3.81 mM