Induction and catabolite repression of glucoamylase formation in Rhizopus chinensis
1988
Wang, H.L.
Rhizopus chinensis, a mold used in oriental food fermentations, produced a low level of constitutive extracellular, intracellular, and cell-bound glucoamylase in a yeast extract-peptone medium. Starch and related polymers induced enzyme formation, but glucose, other easily utilized monosaccharides, and a high concentration of starch repressed enzyme formation. When glucose, either added or derived from starch hydrolysis was utilized during growth, there was relief of repression and enzyme synthesis resumed. The intracellular and cell-bound enzymes were not significantly affected by glucose. R. chinensis produced two forms of glucoamylase, both were glycoproteins, and each had a pH optimum of 4.5 and a temperature optimum of 65.degree. C. The Km values on starch were estimated at 30.0 and 12.8 mg/ml, respectively, and the Vmax values were 57.9 and 30.8 mg glucose formed/min/mg protein.
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