| Summary: | Both nitric oxide (NO) and hydrogen sulfide (H<sub>2</sub>S) 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<sub>2</sub>S 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-<span style="font-variant: small-caps;">l</span>-arginine methyl ester (<span style="font-variant: small-caps;">l</span>-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<sub>2</sub>S metabolism of peaches were studied. The results showed that exogenous NO reduced the contents of endogenous H<sub>2</sub>S, Cys, and sulfite; decreased the activities of <span style="font-variant: small-caps;">l</span>-/<span style="font-variant: small-caps;">d</span>-cysteine desulfhydrase (<span style="font-variant: small-caps;">l</span>-/<span style="font-variant: small-caps;">d</span>-CD), <i>O</i>-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<sub>2</sub>S content by sustaining the activities of <span style="font-variant: small-caps;">l</span>-/<span style="font-variant: small-caps;">d</span>-CDs, OAS-TL, and SiR. <span style="font-variant: small-caps;">l</span>-NAME increased the H<sub>2</sub>S content, mainly by maintaining the <span style="font-variant: small-caps;">d</span>-CD activity. The results suggest that NO, c-PTIO, <span style="font-variant: small-caps;">l</span>-NAME, and sodium tungstate differently regulate the H<sub>2</sub>S metabolism of peaches during storage.
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