Inactivation Kinetics of Polyphenol Oxidase from Pupae of Blowfly (Sarcophaga bullata) in the Dimethyl Sulfoxide Solution

• DOI: 10.1007/s12010-009-8714-9
• Publication Date: 2009-08-07T04:27:03Z
• Authors: Chao-Qi Chen; Zhi-Cong Li; Zhi-Zhen Pan; Yu-Jing Zhu; Ruo-Rong Yan; Qin Wang; Jiang-Hua Yan; Qing-Xi Chen
• Keywords: 0303 health sciences; 571; Polyphenol oxidase; Diptera; Pupa; Stereoisomerism; Dimethyl sulfoxide; Inactivation; Dihydroxyphenylalanine; Enzyme Activation; Solutions; Blowfly pupae; Kinetics; Structure-Activity Relationship; 03 medical and health sciences; Animals; Dimethyl Sulfoxide; Oxidation-Reduction; Catechol Oxidase

The effects of dimethyl sulfoxide (DMSO) on the activity of polyphenol oxidase (PPO, EC 1.14.18.1) from blowfly pupae for the oxidation of L-3,4-dihydroxyphenylalanine were studied. The results showed that low concentrations of DMSO could lead to reversible inactivation to the enzyme. The IC(50) value, the inactivator concentration leading to 50% activity lost, was estimated to be 2.35 M. Inactivation of the enzyme by DMSO was classified as mixed type. The kinetics of inactivation of PPO from blowfly pupae in the low concentrations of DMSO solution was studied using the kinetic method of the substrate reaction. The rate constants of inactivation were determined. The results show that k(+0) was much larger than k'(+0), indicating that the free enzyme molecule was more fragile than the enzyme-substrate complex in the DMSO solution. It was suggested that the presence of the substrate offers marked protection of this enzyme against inactivation by DMSO.