Glycine Metabolism

Abstract

The pyridoxal phosphate-containing glycine decarboxylase from Peptococcus glycinophilus exhibited fluorescence emission peaks at 390 and 500 mµ when activated at 340 and 420 mµ, respectively. Removal of the pyridoxal phosphate resulted in the loss of the 500 mµ peak, but did not affect the 390 mµ peak. When the holoenzyme was reduced with sodium borohydride only a single emission peak at 390 mµ was detectable, but the intensity of the emission was approximately 10-fold greater than the emission at 390 mµ of the nonreduced holoenzyme or of either the reduced or nonreduced apoenzyme. Estimation of the molar ratio of pyridoxal phosphate to enzyme protein was achieved by comparing the increase in fluorescence at 390 mµ, the increase in ultraviolet absorption at 430 mµ, and the increase in catalytic activity of a known amount of apoenzyme upon incubation with increasing amounts of pyridoxal phosphate. It was found that each mole of enzyme bound 2 moles of pyridoxal phosphate.