Studies on decarboxylating enzymes. XVIII. L-glutamate decarboxylase. Determination of the Michaelis-Menten constant. Its use in the titration of pyridoxal-5-phosphate

Abstract

The Michaelis constant of L.glu\amate decarboxylase of Lupi1'11US albus has been determinated. In the experimental con- ditions, we have found the values of Km = 5,5 x 10-3 M for the seed extract and Km = 2,2 x 10-2 M in the case of the enzyme partially purified. The study has been carried out em- ploying the Warburg manometric technique.

The enzyme preparation can be used for the accurate enzy- matic measurement of pyridoxal-5-phosphate in amounts ran- ging from 0.3 to 1.5 μg per ml.