GENETIC ALTERATION OF PYRROLINE-5-CARBOXYLATE REDUCTASE IN NEUROSPORA CRASSA

Abstract

A structural altera-tion of pyrroline-5-carboxylate reductase probably takes place, possibly at its catalytic site, following a single-gene mutation at the prol-1 locus of Neurospora crassa. The alternate results in a 3- to 4-fold increase in activation energy of the reaction and a marked decrease in thermostability of the enzyme in the temperature range tested. In addition, heat inactivation of the mutant enzyme shows a higher degree of temperature dependence than does that of the wild-type enzyme. Several other characteristics of the enzyme examined remain essentially unaltered. The enzyme alteration is accompanied by a marked decrease in specific reductase activity, and it is suggested that a qualitative enzyme change may prove to be a rather frequent consequence of single-gene mutations in which activity of a specific enzyme is known to be very low or "lacking".[long dash]MDS.