5‐Aminolevulinic‐Acid Synthetase of <i>Rhodopseudomonas spheroides</i> Y

Abstract

The two species of 5‐aminolevulinic acid synthetase were purified about 4200‐fold for fraction I and about 2000‐fold for fraction II. They were obtained homogenous in disc electrophoresis. These two enzymes have the same molecular weight (about 100 000) and contain one molar equivalent of pyridoxal phosphate. This cofactor is linked as a substituted aldamine derivative (330 nm) at neutral pH values and as an easily dissociable Schiff base in the acid or very basic ranges. An –SH group may be involved in the formation of the aldamine derivative. They differ by their isoelectric point (p I = 5.1 for fraction I and p I = 6.0 for fraction II) and by their number of –SH groups (1 for fraction I and 7 for fraction II). The results suggest that the two synthetases are two isofunctional enzymes.