6-ALPHA-METHYLHYDROCORTISONE 1-EN-DEHYDROGENATION BY ARTHROBACTER-GLOBIFORMIS-193 CELLS

Some peculiarities of 6 alpha-methylhydrocortisone 1-en-dehydrogenatio n by Arthrobacter globiformis 193 cells have been studied. The introdu ction of an additional methyl group into the hydrocortisone molecule c hanges the biochemical characteristics of the microbiological 1-en-deh ydrogenation. The process as a whole follows substrate inhibition kine tics rather than Michaelis-Menten kinetics. A mathematical model for 6 alpha-methylhydrocortisone 1-en-dehydrogenation by whole cells which describes multiple uncompetitive inhibition by the substrate is propos ed. All kinetic parameters of this reaction have been estimated. The r elationship between the substrate 1-en-dehydrogenation and oxygen cons umption has been studied. The inhibiting effect of 6 alpha-methylhydro cortisone appears at the level of electron transfer along the respirat ory chain. At low substrate concentrations (up to 1.06 mM), when the i nhibitory effect is virtually absent, the reaction rate is determined by enzyme-substrate interaction rather than by respiratory chain activ ity.