Abstract：
Ochratoxin A (OTA) is a toxic secondary metabolite that widely contaminates agro-products and poses a significant dietary risk to human health. Previously, a carboxypeptidase CP4 was characterized for OTA degradation in Lysobacter sp. CW239, but the degradation activity was much lower than its host strain CW239. In this study, an amidohydrolase ADH2 was screened for OTA hydrolysis in this strain. The result showed that 50 μg/L OTA was completely degraded by 1.0 μg/mL rADH2 within 5 min, indicating ultra-efficient activity. Meanwhile, the two hydrolases (i.e., CP4 and ADH2) in the strain CW239 showed the same degradation manner, which transformed the OTA to ochratoxin α (OTα) and l-β-phenylalanine. Gene mutants (Δcp4, Δadh2 and Δcp4-adh2) testing result showed that OTA was co-degraded by carboxypeptidase CP4 and amidohydrolase ADH2, and the two hydrolases are sole agents in strain CW239 for OTA degradation. Hereinto, the ADH2 was the overwhelming efficient hydrolase, and the two types of hydrolases co-degraded OTA in CW239 by synergistic effect. The results of this study are highly significant to ochratoxin A contamination control during agro-products production and postharvest.
摘要：
曲霉毒素A（OTA）是一种有毒的次级代谢产物，广泛污染农产品，对人类健康构成重大饮食风险。以前,羧肽酶CP4在溶杆菌中的OTA降解表征。CW239，但降解活性远低于其宿主菌株CW239。在这项研究中,在该菌株中筛选用于OTA水解的酰胺水解酶ADH2。结果表明，50μg/L的OTA在5min内被1.0μg/mL的rADH2完全降解，表明超有效的活动。同时,两种水解酶(即，CP4和ADH2)在菌株CW239中表现出相同的降解方式，将OTA转化为曲霉毒素α（OTα）和1-β-苯丙氨酸。基因突变（Δcp4，Δadh2和Δcp4-adh2）测试结果表明，OTA被羧肽酶CP4和酰胺水解酶ADH2共降解，这两种水解酶是菌株CW239降解OTA的唯一试剂。在此，ADH2是压倒性的高效水解酶，两种水解酶协同降解CW239中的OTA。这项研究的结果对农产品生产和采后的曲霉毒素A污染控制具有重要意义。
