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Inactivation of Monomeric Sarcosine Oxidase by Reaction with N-(Cyclopropyl)glycine
Journal article   Peer reviewed

Inactivation of Monomeric Sarcosine Oxidase by Reaction with N-(Cyclopropyl)glycine

Gouhua Zhao, Junya Qu, Franklin A Davis and Marilyn Schuman Jorns
Biochemistry (Easton), v 39(46), pp 14341-14347
21 Nov 2000
PMID: 11087383

Abstract

Monomeric sarcosine oxidase (MSOX) catalyzes the oxidative demethylation of sarcosine (N-methylglycine) and contains covalently bound flavin adenine dinucleotide (FAD). The present study demonstrates that N-(cyclopropyl)glycine (CPG) is a mechanism-based inhibitor. CPG forms a charge transfer complex with MSOX that reacts under aerobic conditions to yield a covalently modified, reduced flavin (λmax = 422 nm, ε422 = 3.9 mM-1 cm-1), accompanied by a loss of enzyme activity. The CPG-modified flavin is converted at an 8-fold slower rate to 1,5-dihydro-FAD (EFADH2), which reacts rapidly with oxygen to regenerate unmodified, oxidized enzyme. As a result, CPG-modified MSOX reaches a CPG-dependent steady-state concentration under aerobic conditions and reverts back to unmodified enzyme upon removal of excess reagent. No loss of activity is observed under anaerobic conditions where EFADH2 is formed in a reaction that goes to completion at low CPG concentrations. Aerobic denaturation of CPG-modified enzyme yields unmodified, oxidized flavin at a rate similar to the anaerobic denaturation reaction, which yields 1,5-dihydro-FAD. The CPG-modified flavin can be reduced with borohydride, a reaction that blocks conversion to unmodified flavin upon removal of excess CPG or enzyme denaturation. The possible chemical mechanism of inactivation and structure of the CPG-modified flavin are discussed.

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Web of Science research areas
Biochemistry & Molecular Biology
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