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. 1970 Feb;116(4):733–743. doi: 10.1042/bj1160733

The chemistry of flavins and flavoproteins. Aerobic photochemistry

G R Penzer 1,*
PMCID: PMC1185419  PMID: 4392239

Abstract

1. When a mixture of FMN and a reducing substrate (e.g. unprotonated amine) is illuminated oxygen is consumed. 2. The rate of oxygen uptake increases as oxygen concentration falls with some substrates (type I reaction), but with other substrates (typically aromatic compounds) the rate falls as the oxygen concentration falls (type II reaction). 3. The kinetics of type I reactions with EDTA, dl-α-phenylglycine and diethanolamine are all consistent with a mechanism in which the rate-determining step, hydrogen abstraction by the FMN triplet, is followed by rapid reoxidation of reduced FMN by oxygen. The reaction is faster at low oxygen concentrations because oxygen quenches the triplet. 4. The sensitivity of reaction rates to substituents in dl-α-phenylglycine can be described by a Hammett ρ value of −0.6. 5. Individual rate constants for quenching and reaction of the FMN triplet with substrate were calculated (2.4×108 and 2.1×107m−1s−1 respectively for EDTA) on the assumption that oxygen quenches the triplet in a diffusion-controlled reaction. 6. The pH-dependences of oxygen uptake rates with six natural amino acids as substrates were measured. 7. Photoinactivations of l-glutamate dehydrogenase and d-amino acid oxidase by FMN were demonstrated.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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