PECULIARITIES OF ASPARTATE KINASE AND HOMOSERINE DEHYDROGENASE ACTIVITIES REGULATION BY AMINO ACIDS IN SPIRULINA PLATENSIS MUTANT STRAINS WITH METHIONINE SUPER SYNTHES

Abstract

The activities of aspartate kinase (AK) and homoserine dehydrogenase (GSDG) have been determined in cells of parental wild strain as well as 30B and 198B mutant strains, received on different stages of Spirulina platensis strain selection with elevated content of methionine in biomass. It was found, that only strain 198B showed considerable increase of AK activity (in 1.8 times) in respect to the wild strain. AKactivity is subject to cumulative inhibition by L-threonine and L-lysine in all strains. However, in mutant 198B inhibition effect of these amino acids on the activity AK is much smaller than the same in the wild strain. There is no essential difference in value of GSDG-activity between investigated strains. It is established, that GSDGactivity is subject to inhibition by L-threonine in all strains. GSDG from wild strain was completely inhibited by L-threonine (5 mM), from 30B strain – on 53%, from 198B strain – only on 21%. GSDG from wild strain and 30B strain was activated by L-isoleucine on 32 and 14%, according. GSDG of 198B mutant was not activated by L-isoleucine, but its had a high stimulatory effect (33%) by L-methionine.