The role of disulfide bonds in a Solanum tuberosum saposin-like protein investigated using molecular dynamics

14C-Isotope Use to Quantify Covalent Reactions between Flavor Compounds and β-Lactoglobulin

A 14C-based method was developed to study the rate and extent of covalent bond formation between β-lactoglobulin and three model flavor compounds: a ketone (2-undecanone UDO), an aldehyde (decanal DAL), an isothiocyanate (2-phenylethyl isothiocyanate PEITC), and an unreactive "methods blank" (decane DEC). Aqueous protein solutions with one of the 14C-labeled model flavor compounds were placed in water baths at 25, 45, and 65 °C for 4 weeks measuring the amount of flavor: protein reaction at 1, 3, 7, 14, 21, and 28 days. UDO showed lowest reactivity (max of 0.9% of added compound reacted), DAL (max of 16.4% reacted), and PEITC (max of 71.8% reacted). All compounds showed a rapid initial reaction rate which slowed after ca. 7 days. It appears that only PEITC (at 65 °C) saturated all potential protein-reactive sites over the storage period.

Structural and biochemical characterization of Arabidopsis alcohol dehydrogenases reveals distinct functional properties but similar redox sensitivity

Alcohol dehydrogenases (ADHs) are a group of zinc-binding enzymes belonging to the medium-length dehydrogenase/reductase (MDR) protein superfamily. In plants, these enzymes fulfill important functions involving the reduction of toxic aldehydes to the corresponding alcohols (as well as catalyzing the reverse reaction, i.e., alcohol oxidation; ADH1) and the reduction of nitrosoglutathione (GSNO; ADH2/GSNOR). We investigated and compared the structural and biochemical properties of ADH1 and GSNOR from Arabidopsis thaliana. We expressed and purified ADH1 and GSNOR and determined two new structures, NADH-ADH1 and apo-GSNOR, thus completing the structural landscape of Arabidopsis ADHs in both apo- and holo-forms. A structural comparison of these Arabidopsis ADHs revealed a high sequence conservation (59% identity) and a similar fold. In contrast, a striking dissimilarity was observed in the catalytic cavity supporting substrate specificity and accommodation. Consistently, ADH1 and GSNOR showed strict specificity for their substrates (ethanol and GSNO, respectively), although both enzymes had the ability to oxidize long-chain alcohols, with ADH1 performing better than GSNOR. Both enzymes contain a high number of cysteines (12 and 15 out of 379 residues for ADH1 and GSNOR, respectively) and showed a significant and similar responsivity to thiol-oxidizing agents, indicating that redox modifications may constitute a mechanism for controlling enzyme activity under both optimal growth and stress conditions.

Recent advances and challenges in the interaction between myofibrillar proteins and flavor substances

Myofibrillar proteins are an important component of proteins. Flavor characteristics are the key attributes of food quality. The ability of proteins to bind flavor is one of their most fundamental functional properties. The dynamic balance of release and retention of volatile flavor compounds in protein-containing systems largely affects the sensory quality and consumer acceptability of foods. At present, research on flavor mainly focuses on the formation mechanism of flavor components, while there are few reports on the release and perception of flavor components. This review introduces the composition and structure of myofibrillar proteins, the classification of flavor substances, the physical binding and chemical adsorption of myofibrillar proteins and volatile flavor substances, as well as clarifies the regulation law of flavor substances from the viewpoint of endogenous flavor characteristics and exogenous environment factors, to provide a theoretical reference for the flavor regulation of meat products.