PARTIAL-PURIFICATION AND PROPERTIES OF LATHYRINE SYNTHASE

The enzyme catalysing the simultaneous decarboxylation of 2-amino-4-carboxypyrimidine and its condensation with serine to form lathyrine [beta-(2-aminopyrimidin-4-yl)alanine] has been partially purified (150-fold) by selective heat denaturation, fractionation with ammonium sulphate, and affinity chromatography on a column of avidin (monomeric)-agarose. In addition to a requirement for pyridoxal 5-monophosphate, the enzyme is stimulated by biotin and inhibited by avidin. It exhibits a bimodal pH optimum curve with a major peak at pH 4.5 and a secondary peak at pH 7.2. CoA, ATP and a range of metal ions were without effect. The activity of the enzyme was assayed by incorporation of [3-C-14]serine into lathyrine, isolated by sequential chromatography and electrophoresis.