Oxydationsfermente aus Schimmelpilzen und Hefen. I. Über die Glykolico-Dehydrase der Schimmelpilze

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Abstract
A glycolic dehydrase which also attacks lactic acid was detected in a number of moulds belong to the phycomycetes, ascomycetes and fungi imperfecti. The enzyme present in extracts of Aspergillus fumigatus was investigated in some detail. The activity of the extract varied with the carbon source of the medium; when glycolic acid or lactic acid was present the activity was over 100 times greater than with glucose. The enzyme reacted with a large number of hydrogen acceptors including ferricyanide, quinone, tetrazolium salts and dyes including those of the indigo sulphonate series. The enzyme also reacted with oxygen, but this activity was variable and decreased on dialysis; it is probably of a more complex nature. In spite of the fact that glycolic acid is a more efficient inducer, lactic acid is dehydro-genated more rapidly. The Michaelis constants for the two substrates are the same and lie between 0.5 and 1.0 x 10-3 M. The pH optimum is between pH 6 and 8.5. The enzyme is re-markably heat-labile, being inactivated at 36[degree]C. Dialysis in the cold causes a slow inactivation which is not reversed by pyridine or flavin nucleotides. If the enzyme contains a flavin, like the plant enzyme, it has a very low dissociation constant. The product of the dehydrogenation of glycolic acid is glyoxylic acid, which is not further attacked.