Abstract: This study aimed to evaluate the enzymatic properties and inducible expression efficiency of nitric oxide synthase (NOS) produced by Staphylococcus xylosus ATCC 29971, and to explore the effects of different inducers on the color development capacity of the strain by regulating NOS activity in a metmyoglobin model system. Results showed that NOS exhibited the highest catalytic activity at 45 ℃, with an optimal pH of 7.0, and maintained favorable stability even at pH 4.0. Na+ exerted a significant inhibitory effect on NOS activity, whereas Ca2+ effectively enhanced NOS activity (P < 0.05). The maximum reaction velocity and Michaelis constant of NOS were determined to be 0.90 μmol/(L·min) and 9.98 μmol/L, respectively. Ascorbic acid and L-arginine showed the most prominent enhancing effects on NOS activity at 1 mmol/L and 50 mmol/L, respectively (P < 0.05). Among three sugars tested, sucrose (5%) was the most effective inducer of NOS. In the metmyoglobin model system, these inducers significantly increased the a* value and strengthened the intensity of the characteristic absorption peaks at 542 and 581 nm. These findings indicated that the inducers could effectively facilitate the conversion of metmyoglobin to nitrosylmyoglobin by improving NOS activity, thereby enhancing the color development. By clarifying the enzymatic properties of NOS from S. xylosus ATCC 29971 and its regulatory strategies for enzyme production, this study provides a valuable reference for color development and functional applications in low-nitrite fermented meat products.

Key words: Staphylococcus xylosus; nitric oxide synthase; enzymatic properties; induced expression; color development