Abstract：
Salt-tolerant proteases with remarkable stability are highly desirable biocatalysts in the salt-fermented food industry. In this study, the undigested autocleavage product of HlyA (halolysin A), a low-salt adapted halolysin from halophilic archaeon Halococcus salifodinae, was investigated. HlyA underwent autocleavage of its C-terminal extension (CTE) at temperatures over 40 °C or NaCl concentrations below 2 M to yield HlyAΔCTE. HlyAΔCTE demonstrated robust stability over a wide range of -20-60 °C, 0.5-4 M NaCl, and pH 6.0-10.0 for at least 72 h. Notably, HlyAΔCTE is the first reported halolysin with such exceptional stability. Compared with HlyA, HlyAΔCTE preferred high temperatures (50-75 °C), low salinities (0.5-2.5 M NaCl), and near-neutral (pH 6.5-8.0) conditions to achieve high activity, consistently with its production conditions. HlyAΔCTE displayed a higher Vmax value against azocasein than HlyA. During fish sauce fermentation, HlyAΔCTE significantly enhanced fish protein hydrolysis, indicating its potential as a robust biocatalyst in the salt-fermented food industry.
摘要：
具有显著稳定性的耐盐蛋白酶是盐发酵食品工业中非常理想的生物催化剂。在这项研究中,未消化的HlyA（卤溶素A）的自切割产物，一种来自嗜盐古细菌Halococcussalifdinae的低盐适应盐溶素，被调查。在超过40°C的温度或低于2M的NaCl浓度下，HlyA经历了其C端延伸（CTE）的自动切割，从而产生了HlyAΔCTE。HlyAΔCTE在-20-60°C的宽范围内表现出强大的稳定性，0.5-4MNaCl,和pH6.0-10.0持续至少72小时。值得注意的是，HlyAΔCTE是第一个报道的具有这种优异稳定性的卤溶素。与HlyA相比,HlyAΔCTE首选高温（50-75°C），低盐度（0.5-2.5MNaCl），和近中性（pH6.5-8.0）条件，以实现高活性，与其生产条件一致。HlyAΔCTE对偶氮酪蛋白的Vmax值高于HlyA。在鱼露发酵过程中，HlyAΔCTE显着增强鱼类蛋白质水解，表明其作为盐发酵食品工业中强大的生物催化剂的潜力。
