Some properties of glycine aminotransferase purified from Rhodopseudomonas palustris No. 7 concerning extracellular porphyrin production.

Glycine aminotransferase (EC 2.6.1.4; GlyAT) was presumed to be an enzyme concerning the supply of glycine for the extracellular porphyrin production by Rhodopseudomonas palustris No. 7. GlyAT was purified from strain No. 7 as an electrophoretically homogeneous protein. The enzyme was a monomer protein with the molecular weight of about 42,000. From the absorption spectrum of the enzyme (350 run, 410 nm), it was indicated that the enzyme had pyridoxal phosphate as a prosthetic group. The enzyme showed high substrate specificity for glutamate as an amino group donor. Apparent K(m)s for glutamate and glyoxylate were 6.20 mm and 3.75 mm, respectively. The V-max and K-cat for glutamate were 66.8 mumol/min/mg protein and 46.8 s(-1), respectively. The V-max and K-cat for glyoxylate were 68.8 mumol/min/mg protein and 48.2 s(-1). The optimum temperature and pH were 40-45degreesC and 7.0similar to7.5, respectively. The enzyme activity lowered to about 50% in the presence of 15 mm ammonium chloride.