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Besides its amide hydrolase activity, the amidase from Brevibacterium sp. R312 also exhibits an acyl-transferase activity.The mechanism of the transfer reaction of the acyl from acetamide to hydroxylamine was studied. This is a “Bi Bi Ping Pong” type reaction. The kinetic parameters of the reaction were determined: – Apparent Vm = 135 μmol · min –1 · mg–1– Acetamide Km = 18.2 mM– Hydroxylamine Km = 131 mMA reaction mechanism involving the -SH group of the amidase was proposed.

Candida salmenticensis possesses an inductible inulinase of β fructosidase type, also active on raffinose and saccharose. The enzyme resides in the cell wall but is easily excreted into the culture medium during growth. Its principal characteristics for inulin are: optimum pH 3.5– 4, optimum temperature 46°C, good stability at 50°C and Km=1.7 × 10−2 M.

The acetonitrilase from Brevibacterium R 312 has an activity between pH 5 and 10, with an optimum pH of 7, the optimum temperature is between 30° and 35°C. It is a thermolabile enzyme and the temperature denaturation starts at 35°C. The Michaelis constant is near 2,5.10−2 m. The enzyme is localized in the 180 000 g supernatant. It is an non adaptative enzyme.

The mechanism of starch degradation by the yeast Lipomyces starkeyi was studied in strain CBS 1807. It was shown that the amylolytic system is associated with cell walls. It is equally well induced by starch or maltose. The enzyme exhibits considerable α amylase type activity and also liberates a small amount of glucose. Enzyme synthesis occurs during the exponential growth phase. The regulation of the synthesis of the enzyme is discussed.

Isolement, fractionnement et caracterisation de deux enzymes Acetoin deshydrogenases chez Saccharomyces uvarum