Regulation of Hydrogen Sulfide Metabolism by Nitric Oxide Inhibitors and the Quality of Peaches during Cold Storage

Abstract

Both nitric oxide (NO) and hydrogen sulfide (H ₂S) have been shown to have positive effects on the maintenance of fruit quality during storage; however, the mechanisms by which NO regulates the endogenous H ₂S metabolism remain unknown. In this experiment, peaches were immersed in solutions of NO, potassium 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO, as an NO scavenger), N-nitro- l-arginine methyl ester ( l-NAME, as an inhibitor of nitric oxide synthase (NOS)-like activity), and sodium tungstate (as an inhibitor of nitrate reductase), and the resulting changes in the H ₂S metabolism of peaches were studied. The results showed that exogenous NO reduced the contents of endogenous H ₂S, Cys, and sulfite; decreased the activities of l-/ d-cysteine desulfhydrase ( l-/ d-CD), O-acetylserine (thiol)lyase (OAS-TL), and sulfite reductase (SiR); and increased the activity of β-cyanoalanine synthase (β-CAS). Both c-PTIO and sodium tungstate had similar roles in increasing the H ₂S content by sustaining the activities of l-/ d-CDs, OAS-TL, and SiR. l-NAME increased the H ₂S content, mainly by maintaining the d-CD activity. The results suggest that NO, c-PTIO, l-NAME, and sodium tungstate differently regulate the H ₂S metabolism of peaches during storage.