The catalytic role of the copper ligand H172 of peptidylglycine α-hydroxylating monooxygenase: A kinetic study of the H172A mutant

John P. Evans, Ninian Blackburn, Judith P. Klinman

Research output: Contribution to journalArticle

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Abstract

An essential histidine ligand to the electron transfer copper (Cu H) of peptidylglycine α-hydroxylating monooxygenase (PHMcc) was mutated to an alanine and found to retain copper binding and hydroxylase activity [Jaron, S., et al. (2002) Biochemistry 41, 13274-13282]. An extensive kinetic and deuterium isotope effect study finds this mutant to maintain full coupling of O2 consumed to product formed despite a 3 order-of-magnitude decrease in kcat and a 300-fold decrease in k cat/Km(O2). Unexpectedly, electron transfer is not rate-limiting in H172A. Rather, the increased kinetic isotope effect (KIE) on kcat of 3.27 ± 0.39 suggests that C-H bond cleavage has become more rate-limiting, implicating a role for His172 that goes beyond that of a simple ligand to CUH. The mechanistic implications are discussed.

Original languageEnglish (US)
Pages (from-to)15419-15429
Number of pages11
JournalBiochemistry
Volume45
Issue number51
DOIs
StatePublished - Dec 26 2006

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Mixed Function Oxygenases
Isotopes
Copper
Electrons
Ligands
Biochemistry
Kinetics
Deuterium
Histidine
Alanine
Cats
peptidylglycine monooxygenase

ASJC Scopus subject areas

  • Biochemistry

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The catalytic role of the copper ligand H172 of peptidylglycine α-hydroxylating monooxygenase : A kinetic study of the H172A mutant. / Evans, John P.; Blackburn, Ninian; Klinman, Judith P.

In: Biochemistry, Vol. 45, No. 51, 26.12.2006, p. 15419-15429.

Research output: Contribution to journalArticle

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