Promiscuous activity of ornithine decarboxylase from Enterobacter hormaechei: An alternative pathway for histamine formation in fermented sausages.

Authors

Wei He, Binbin Li, Kaidi Hu, Xumei Zhong, Yulin Zhang, Jiamei Yu, Jiaxin Xie, Chengtao Li, Fengqin Li, Lanlan Wu, Shuhong Li, Jianlong Li, Xinjie Hu, Xiaolin Ao, Teng Hui, Ning Zhao, Aiping Liu, Likou Zou, Shuliang Liu, Zhengfeng Fang, Dongdong Wang, Shuxiang Liu, Yong Yang

Published in

Food microbiology. Volume 141. Pages 105248. Epub Jul 23, 2026.

Abstract

Histamine, a toxic biogenic amine in fermented foods, is classically produced by histidine decarboxylase (Hdc). Enterobacter hormaechei RH3 isolated from Sichuan fermented sausages, despite being hdc-deficient (hdc^-), still accumulates high levels of histamine via ornithine decarboxylase (Odc). In this study, Hdc from Enterobacter hormaechei RH15 (hdc⁺) and Odc from RH3 were cloned, characterized, and compared systematically. Hdc displayed strict substrate specificity toward L-histidine with stronger affinity and higher catalytic efficiency (K_m = 126.8 mM, kcat/K_m = 0.00697 mM s^-1; optimum 30 °C, pH 7.0). Odc showed substrate promiscuity toward both L-ornithine and L-histidine (for L-histidine: K_m = 195.4 mM, kcat/K_m = 0.00354 mM s^-1), along with improved thermostability and pH adaptability (optimum 35 °C, pH 6.0). Molecular docking and 100 ns molecular dynamics simulations revealed distinct substrate binding modes and conformational stability, with the C-terminal domain and the positively charged active pocket potentially being the main contributors to Odc's promiscuity. Validation in sausage models demonstrated that Hdc dominated histamine formation, reaching 42 mg/kg at 120 h, while Odc acted as a secondary pathway. This study identifies a non-classical histamine synthesis pathway mediated by Odc, advances the current understanding of microbial histamine metabolism, and provides new insights into controlling biogenic amine accumulation in fermented meat products.

PMID:
42668185
Bibliographic data and abstract were imported from PubMed on 30 Aug 2026.

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