Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Study of enzymatic properties of phenol oxidase from nitrogen-fixing Azotobacter chroococcum | Herter et al. AMB Express 2011 1 14 http content 1 1 14 o AMB Express a SpringerOpen Journal ORIGINAL Open Access Study of enzymatic properties of phenol oxidase from nitrogen-fixing Azotobacter chroococcum 1 2 2 1 1 Susanne Herter Marlen Schmidt Mark L Thompson Annett Mikolasch and Frieder Schauer Abstract Azotobacter chroococcum is a widespread free-living soil bacterium within the genus of Azotobacter known for assimilation of atmospheric nitrogen and subsequent conversion into nitrogenous compounds which henceforth enrich the nitrogen content of soils. A. chroococcum SBUG 1484 isolated from composted earth exhibits phenol oxidase PO activity when growing under nitrogen-fixing conditions. In the present study we provide incipient analysis of the crude PO activity expressed by A. chroococcum SBUG 1484 within comparative analysis to fungal crude PO from the white-rot fungus Pycnoporus cinnabarinus SBUG-M 1044 and tyrosinase PPO from the mushroom Agaricus bisporus in an attempt to reveal desirable properties for exploitation with future recombinant expression of this enzyme. Catalytic activity increased with pre-incubation at 35 C however 70 of activity remained after pre-treatment at 50 C. Native A. chroococcum crude PO exhibited not only strong preference for 2 6-dimethoxyphenol but also towards related methoxy-activated substrates as well as substituted orthobenzenediols from over 40 substrates tested. Presence of CuSO4 enhanced crude phenol oxidase activity up to 30 whereas NaN3 mM was identified as the most inhibiting substance of all inhibitors tested. Lowest inhibition of crude PO activity occurred after 60 minutes of incubation in presence of 15 methanol and ethanol with 63 and 77 remaining activities respectively and presence of DMSO even led to increasing oxidizing activities. Substrate scope and inhibitor spectrum strongly differentiated A. chroococcum PO activity comprised in crude extracts from those of PPO and confirmed .
