Avermectin B2 O-methyltransferase activity in "Streptomyces avermitilis" mutants that produce increased amounts of the avermectins.
AUTOR(ES)
Schulman, M D
RESUMO
The level of activity of avermectin B O-methyltransferase, the enzyme which catalyzes the conversion of avermectin B components to avermectin A components, was analyzed in a series of "Streptomyces avermitilis" mutants selected for increased production of the avermectins. In all of the mutants, increased avermectin production was accompanied by increased avermectin B O-methyltransferase activity. Both the average specific activity and the maximum observed specific activity of avermectin B O-methyltransferase increased in direct proportion to avermectin production. The level of avermectin B O-methyltransferase alone did not determine the extent of conversion of avermectin B components to avermectin A components, since a constant ratio of B components to A components was maintained throughout the fermentation even though avermectin B O-methyltransferase specific activity varied three- to fivefold. These results indicate that avermectin B O-methyltransferase is not rate limiting. The correlation between avermectin B O-methyltransferase specific activity and avermectin production is compatible with the hypothesis that genes coding for successive steps in the same secondary metabolite biosynthetic pathway are coordinately regulated.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=180454Documentos Relacionados
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