Sorbitol Dehydrogenase Membrane Bound

Sorbitol ^ L-sorbose

Unlike the ubiquitous quinoprotein polyol dehydrogenases in acetic acid bacteria, one of which catalyzes oxidation of D-sorbitol to L-sorbose, a distinct D-sorbitol dehydrogenase (SLDH) was found in the membrane fraction of G. suboxydans var. a IFO 3254. SLDH was solubilized from the membrane fraction and purified as a covalently bound FAD-containing dehydrogenase [67]. The best solubilization of SLDH carried out in 10 mmol L-1 acetate, pH 5.0, containing 1% Triton X-100, 0.1 mol L-1 KCl, and 0.1 mol L-1 D-sorbitol gave the highest recovery of more than 100%. Purification of SLDH was readily done by DEAE-cellulose and CM-cellulose chromatography. The purified SLDH showed a rose-red color due to the presence of heme c and the absorption spectrum of SLDH after reduction with sodium dithionite gave absorption maxima at 551, 522, and 417 nm in the visible region. The heme c component was not reduced rapidly by the addition of D-sorbitol, primary substrate, until coenzyme Q1 was added to the enzyme solution, implying that ubiquinone mediates D-sorbitol oxidation, similar to the other membrane-bound dehydrogenases exemplified in this article.

SLDH dissociated into three subunits of 63 kDa (subunit I), 51 kDa (subunit II), and 17 kDa (subunit III). Subunit I was characterized as a flavoprotein and FAD was bound covalently to the enzyme. Subunit II contained heme c. SLDH catalyzes D-sorbitol oxidation to L-sorbose exclusively, which is distinct from PQQ-dependent polyol dehydrogenases catalyzing D-sorbitol oxidation to L-sorbose. The substrate specificity is restricted to D-sorbitol, and D-mannitol was oxidized only by 5% of that of D-sorbitol. Other polyols, such as D-arabitol, D-iditol, meso-erythritol, dulcitol, ribitol, and xylitol, are not oxidized by the enzyme.

Heal Yourself With Qi Gong

Heal Yourself With Qi Gong

Qigong also spelled Ch'i Kung is a potent system of healing and energy medicine from China. It's the art and science of utilizing breathing methods, gentle movement, and meditation to clean, fortify, and circulate the life energy qi.

Get My Free Ebook

Post a comment