Activity of threonine deaminase and biosynthesis of avermectins in the culture of Streptomyces avermitilis

: The influence of ammonium, threonine, isoleucine and valine on the activity of threonine deaminase and the biosynthesis of avermectins in the culture of two mutants of Streptomyces avermitilis, i.e. a sensitive one and a resistant one with respect to alpha-amino-beta-oxyvaleric acid, a threonine antimetabolite, was studied. It was shown that the synthesis of threonine deaminase was induced by threonine and valine in the mycelium of both the mutants. The level of threonine deaminase was higher in the mycelium of the antimetabolite resistant mutant. The antibiotic activity of the resistant mutant was lower while the relative content of the group B avermectins in the pool of the synthesized avermectins was higher than that in the culture of the sensitive mutant.