Mechanisms of Cytochrome P450-Catalyzed Oxidations

Abstract

Enzymes are complex biological catalysts and are critical to life. Most oxidations of chemicals are catalyzed by cytochrome P450 (P450, CYP) enzymes, which generally utilize mixed-function oxidase stoichiometry, utilizing pyridine nucleotides as electron donors: NAD(P)H + O2 + R → NAD(P)+ + RO + H2O (where R is a carbon substrate and RO is an oxidized product). The catalysis of oxidations is largely understood in the context of the heme iron-oxygen complex generally referred to as Compound I, formally FeO3+, whose basis was in peroxidase chemistry. Many X-ray crystal structures of P450s are now available (≥ 822 structures from ≥146 different P450s) and have helped in understanding catalytic specificity. In addition to hydroxylations, P450s catalyze more complex oxidations, including C-C bond formation and cleavage. Enzymes derived from P450s by directed evolution can even catalyze more unusual reactions, e.g. cyclopropanation. Current P450 questions under investigation include the potential role of the intermediate Compound 0 (formally FeIII-O2−) in catalysis of some reactions, the roles of high- and low-spin forms of Compound I, the mechanism of desaturation, the roles of open and closed structures of P450s in catalysis, the extent of processivity in multi-step oxidations, and the role of the accessory protein cytochrome b5. More global questions include exactly how structure drives function, prediction of catalysis, and roles of multiple protein conformations.

Riboflavin Directly Mediates the Dealkylation by Microbial Cytochrome P450 Monooxygeneses

“…Further thorough comparison revealed that this finding is mediated by a new electron transfer pathway, which is not the same as any reported mechanisms for P450s. 30 Subsequently, based on sequence alignments with other microbial P450s, we found that residue Leu340 of HmtS is different from other enzymes. Thus, HmtS-L340F mutant was constructed to show higher catalytic efficiency.…”

Broadening the Scope of Biocatalysis in Sustainable Organic Synthesis

“…The most well‐known and extensively studied oxygenases are the cytochrome (Cyt) P450‐dependent monooxygenases that catalyze, among other reactions, regio‐ and stereoselective hydroxylations of alkanes, alkenes and aromatic hydrocarbons. It has been estimated that around 95 % of all enzyme‐catalyzed oxidations reported in the literature involve Cyt P450s . Indeed, the steroid hydroxylations developed in the middle of the last century (see Section 1) involved catalysis by Cyt P450s.…”

“…oxidations reported in the literature involve Cyt P450s. [163] Indeed, the steroid hydroxylationsd eveloped in the middle of the last century( see Section 1) involved catalysis by Cyt P450s. The latter are multicomponent biocatalysts in which reducing equivalents are provided by NAD(P)H indirectly to the P450 through am ediator, which can be af lavin or ferredoxin (see Scheme 20).…”

M−O Bonding Beyond the Oxo Wall: Spectroscopy and Reactivity of Cobalt(III)‐Oxyl and Cobalt(III)‐Oxo Complexes

“…[1,2] When progressing to late transition metals,t he occupancyo fp-antibonding metal do rbitals increases,a nd metal-oxo bonds become weaker and more reactive.T his culminates in the rich chemistry of iron-oxo compounds,s uch as heme (P450) [3][4][5] and non-heme iron enzymes [6,7] that inspired the development of important C À H oxidation catalysts. [1,2] When progressing to late transition metals,t he occupancyo fp-antibonding metal do rbitals increases,a nd metal-oxo bonds become weaker and more reactive.T his culminates in the rich chemistry of iron-oxo compounds,s uch as heme (P450) [3][4][5] and non-heme iron enzymes [6,7] that inspired the development of important C À H oxidation catalysts.…”

“…Theterminal oxo ligand is astrong p donor that can form metal-oxo triple bonds with early transition metals such as in VO 2+ or MoO 3+ . [1,2] When progressing to late transition metals,t he occupancyo fp-antibonding metal do rbitals increases,a nd metal-oxo bonds become weaker and more reactive.T his culminates in the rich chemistry of iron-oxo compounds,s uch as heme (P450) [3][4][5] and non-heme iron enzymes [6,7] that inspired the development of important C À H oxidation catalysts. [8][9][10] In contrast, metal-oxo complexes beyond Group 8a re rare and exist only in square-pyramidal, [11] trigonal-pyramidal, [12,13] and, importantly,s quare-planar [14] coordination geometries in which electrons occupy MÀ On on-bonding (or weakly p * -antibonding) do rbitals.S tabilization of metal-oxo complexes beyond Group 8h as also been achieved by coordination of oxygen to Lewis acids.…”