Kinetic Behavior of Desulfovibrio gigas Aldehyde Oxidoreductase Encapsulated in Reverse Micelles

S.L.A. ANDRADE; C.D. BRONDINO; E.O. KAMENSKAYA; A.V. LEVASHOV; I. MOURA; J.J.G. MOURA,

BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS

Elsevier

Año: 2003 vol. 308 p. 73 - 78

0006-291X

We report the kinetic behavior of the enzyme aldehyde oxidoreductase (AOR) from the sulfate reducing bacterium Desulfovibrio gigas (Dg) encapsulated in reverse micelles of sodium bis-(2-ethylhexyl) sulfosuccinate in isooctane using benzaldehyde, octaldehyde, and decylaldehyde as substrates. Dg AOR is a 200-kDa homodimeric protein that catalyzes the conversion of aldehydes to carboxylic acids. Ultrasedimentation analysis of Dg AOR-containing micelles showed the presence of 100-kDa molecular weight species, confirming that the Dg AOR subunits can be dissociated. UV–visible spectra of encapsulated Dg AOR are indistinguishablefrom the enzyme spectrum in solution, suggesting that both protein fold and metal cofactor are kept intact upon encapsulation. The catalytic constant (kcat) profile as a function of the micelle size W0 (W0 ¼ ½H2O/[AOT]) using benzaldehyde as substrate showed twobell-shaped activity peaks at W0 ¼ 20 and 26. Furthermore, enzymatic activity for octaldehyde and decylaldehyde was detected only in reverse micelles. Like for the benzaldehyde kinetics, two peaks with both similar kcat values and W0 positions were obtained. EPR studies using spin-labeled reverse micelles indicated that octaldehyde and benzaldehyde are intercalated in the micelle membrane. This suggests that, though Dg AOR is found in the cytoplasm of bacterial cells, the enzyme may catalyze the reaction of substrates incorporated into a cell membrane.