FORMATE DEHYDROGENASE IN A REVERSED MICELLE SYSTEM - REGULATION OF CATALYTIC ACTIVITY AND OLIGOMERIC COMPOSITION OF THE ENZYME

Formate dehydrogenases from the methylotrophic bacteria Pseudomonas sp . 101 and Mycobacterium vaccae N10 were studied in a system of Aerosol OT reversed micelles in octa ne. Th ree pea ks of the catalytic activ ity were found on the plot of activity versus surfactant hydration deg ree (the size of the micellar inner cavity) which corresponded to func tions of the enzyme in various oligomeric forms: monomeric, dimeric, a nd octameric. Kinetic data were confirmed by results of sedimentation analysis. The enzyme was chemically modified by a bifunctional reagent (dimethyl suberimidate) to obtain a catalytically active non-dissocia ting dimeric molecule of formate dehydrogenase. In the case of the cov alently-linked non-dissociating dimeric enzyme, the peak which corresp onded to the monomeric form of the enzyme was found to disappear from the catalytic activity curve.