Sorbitol dehydrogenase (SDH) serves as a critical enzyme in the polyol pathway, an alternative metabolic route diverging from glycolysis. In this study, SDH was extracted and purified from chicken liver using a two-step chromatographic procedure involving DEAE-Sephadex anion exchange chromatography followed by Sephadex G-100 gel filtration. Molecular characterization determined that the enzyme’s subunit weight is approximately 41.4 kDa, while the native enzyme exists as a tetramer with a total molecular weight of 169 kDa, as confirmed by SDS-PAGE and gel filtration analyses. The enzyme exhibited peak catalytic activity under alkaline conditions, with an optimal pH of 9.0 and a temperature optimum of 50°C. The inhibitory impact of several heavy metal ions—including Cd²⁺, Pb²⁺, Hg²⁺, Ag⁺, Zn²⁺, and Ni²⁺—on SDH activity was evaluated. Among these, cadmium ions demonstrated the most potent inhibition, with an IC₅₀ value of 0.006 mM. Further studies using Lineweaver-Burk plots showed that the inhibition values were 0.07033 ± 0.00287 mM for Cd²⁺, 0.18033 ± 0.04879 mM for Pb²⁺, and 2.112 ± 0.03716 mM for Zn²⁺. The data unequivocally identify Cd²⁺ as the most effective inhibitor of sorbitol dehydrogenase (SDH) among the heavy metals analyzed, characterized by its remarkably low IC₅₀ value.
Akkuş et al. (Sat,) studied this question.