Abstract
Arginine decarboxylase (E.C. 4.1.1) after purification from rice seedlings was separated into fractions A (MW 88000) and B (MW 174000) by gel chromatography. Fraction B was much more active than A. After DEAE cellulose chromatography, the active fraction of the enzyme (B) was purified to homogeneity, which appeared as a single band in gel electrophoresis. The optimal pH and temperature for the enzyme were 8.0 and 45°C respectively. The enzyme followed typical Michaelis-Menten kinetics with a Km value of 0.28 mM. It had no dependence on a metal, and consisted of 16 amino acids of which proline was prominent. Pyridoxal-5-phosphate acted as a cofactor of the enzyme. The enzyme activity was inhibited by various amines and inhibitors, of which the highest inhibition was obtained with spermine and hydroxylamine. The plant hormones played a vital role in regulating the activity of the enzyme which was promoted by kinetin and inhibited by abscisic acid.
