ISOENZYMES OF ACID RIBONUCLEASE IN COTYLEDONS OF PISUM-SATIVUM-L

Acid ribonuclease from cotyledons of P. sativum is very stable, with a temperature optimum of 65.degree. C. It has a MW of 17,500 and there is evidence that a fragment, with a molecular weight of 3100, retains enzyme activity. Acid ribonuclease from the cotyledons of 5-day old seedlings may be fractionated into 2 iso-enzymes, I and II, by CM-cellulose chromatography. The increase in activity of iso-enzyme I is not inhibited by cycloheximide, whereas the increase in iso-enzyme II activity is strongly inhibited by cycloheximide. Cotyledons of 9-day old seedlings contain only iso-enzyme I, while cotyledons of 15 day old seedlings contain 3 iso-enzymes, I, IIa and III.