Abstract
Many thiol-containing molecules show heavy metal complexation ability and are used as antidotes. In this study, the potential function associated with thiol-containing peptides (TCPs) from soy protein hydrolysates as natural detoxicants for heavy metals is reported. TCPs enriched by Thiopropyl-Sepharose 6B covalent chromatography had different molecular weight distributions as well as different numbers of proton dissociable groups, depending on the proteases and degree of hydrolysis. The major contribution of sulfhydryl groups was confirmed by the largest pH decrease between 8.0 and 8.5 of the pH titration curves. The complexation of TCPs with heavy metalswas evaluated by stability constants (βn) of TCP-metal complexes whose stoichiometry was found to be 1:1 (ML) and 1:2 (ML2). TCPs from degree of hydrolysis of 25% hydrolysates gave high affinities towards Hg2+, Cd2+, and Pb2+ (giving similar or even bigger lgβ values than that of glutathione). A significantly positive correlation was found between the logarithm of stability constants for ML2 (lgβ2) and the sulfhydryl group content. Molecular weight distribution of TCPs affected the complexation with Pb2+ notably more than Hg2+ and Cd2+. These results suggest that soy TCPs have the potential to be used in the formulation of functional foods to counteract heavy metal accumulation in humans.
Highlights
With the rapid industrialization and urbanization, pollution from heavy metals has become a serious threat to public health
The results suggested that the heavy metal chelating ability of thiol-containing peptides (TCPs) was affected by the content of the sulfhydryl group, and depended on the global structure of the peptides
(r = 681, p < 0.05 for lgβ1 and r = 0.835, p < 0.01 for lgβ2). These results indicated that the molecular weight (Mw) distribution affected interactions between TCPs and Pb2+ more notably than the other two metal ions
Summary
With the rapid industrialization and urbanization, pollution from heavy metals has become a serious threat to public health. PCs are a family of short cysteine-rich metal-chelating peptides with a structure of γGlu-CysnGly, where, n varies from 2 to 11 depending on the species and conditions of exposure to metal ions [8]. They primarily form a Mw 3600 Da complex with cadmium [9]. Atabey et al [29] and Gamov et al [30] determined the stability constants of aurintricarboxylic acid, and nicotinamide-heavy metal complexes using the potentiometric titration method. The results of this study may provide insight into soy protein hydrolysates as detoxication agents for heavy metal poisoning
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