Steady-state kinetic properties of sorbitol dehydrogenase from chicken liver

Karacaoglan V., Ozer I.

COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY, vol.140, no.2, pp.309-312, 2005 (SCI-Expanded) identifier identifier identifier


The steady-state kinetic properties of partially purified chicken liver sorbitol dehydrogenase (SDH) were determined spectrophoto-metrically at 25degreesC, in 50 mM 3-(N-morpholino)propanesulfonic acid (MOPS) buffer, pH 8.0. In the sorbitol-to-fructose direction, analysis was based on initial rate data obtained at [NAD(+)](o) = 0.1-0.4 mM and [sorbitol](o) = 1.25-10 mM. The reverse process was analyzed by recording progress curves for NADH consumption, starting with [NADH](o) = 0.2 mM and [fructose](o) = 66.7-267 mM. The kinetics conformed to an ordered sequential model, with the cofactors adding first. The steady-state parameters in the forward direction. KNAD-, KiNAD- and K-sorbitol, were found to be 210 +/- 62 muM. 220 +/- 69 muM and 3.2 +/- 0.54 mM, respectively. The corresponding parameters in the reverse direction were K-NADH = 240 +/- 58 muM, K-iNADH = 10 +/- 2.8 muM and K-fructose = 1000 +/- 140 mM. The results indicated a close parallelism with human SDH, yet up to 40-fold differences were observed when compared to related reports on other mammalian species. The structural and adaptive bases of the variation in substrate and cofactor affinities need to be accounted for. (C) 2004 Elsevier Inc. All rights reserved.