title: Inactivation kinetics of polyphenol oxidase from pupae of blowfly (Sarcophaga bullata) in the dimethyl sulfoxide solution.
abstract: 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.
authors: College of Urban and Environmental Sciences, Peking University, Peking 100871, China.
authors: Chao-Qi
authors: CQ
authors: Chen
authors: Zhi-Cong
authors: ZC
authors: Li
authors: Zhi-Zhen
authors: ZZ
authors: Pan
authors: Yu-Jing
authors: YJ
authors: Zhu
authors: Ruo-Rong
authors: RR
authors: Yan
authors: Qin
authors: Q
authors: Wang
authors: Jiang-Hua
authors: JH
authors: Yan
authors: Qing-Xi
authors: QX
authors: Chen
mesh_terms: D000818:Animals; D004156:Catechol Oxidase / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D004295:Dihydroxyphenylalanine / Q000737:chemistry; D004121:Dimethyl Sulfoxide / Q000737:chemistry / Q000494:pharmacology*; D004175:Diptera / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D010084:Oxidation-Reduction / Q000187:drug effects; D011679:Pupa / Q000201:enzymology; D012996:Solutions; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D012996:Solutions; D004295:Dihydroxyphenylalanine; D004156:Catechol Oxidase; D004121:Dimethyl Sulfoxide