Literature summary for 4.1.99.13 extracted from

Schleicher, E.; Hitomi, K.; Kay, C.W.; Getzoff, E.D.; Todo, T.; Weber, S.
Electron nuclear double resonance differentiates complementary roles for active site histidines in (6-4) photolyase (2007), J. Biol. Chem., 282, 4738-4747.

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Cloned(Commentary)

Cloned (Comment)	Organism
cloned and overexpressed in Escherichia coli	Xenopus laevis

Protein Variants

Protein Variants	Comment	Organism
H354A	mutation of a conserved His residue: mutant is inactive in photorepair	Xenopus laevis
H358A	mutation of a conserved His residue: mutant is inactive in photorepair	Xenopus laevis

Organism

Organism	UniProt	Comment	Textmining
Xenopus laevis	-	-	-

Reaction

Reaction	Comment	Organism	Reaction ID
(6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA)	The overall repair reaction consists of two distinct steps, one of which is light-independent and the other one light-dependent. In the initial light-independent step, a 6-iminium ion is thought to be generated via proton transfer induced by two histidines highly conserved among the (6-4) photolyases.This intermediate spontaneously rearranges to form an oxetane intermediate by intramolecular nucleophilic attack. In the subsequent light-driven reaction, one electron is believed to be transferred from the fully reduced FAD cofactor (FADH-) to the oxetane intermediate thus forming a neutral FADH radical and an anionic oxetane radical, which spontaneously fractures. The excess electron is then back-transferred to the flavin radical restoring the fully reduced flavin cofactor and a pair of pyrimidine bases	Xenopus laevis	a

Substrates and Products (Substrate)

Substrates	Comment Substrates	Organism	Products	Comment (Products)	Rev.	Reac.
additional information	(6-4) photolyase is examined by optical spectroscopy, electron paramagnetic resonance, and pulsed electron nuclear double resonance spectroscopy. It is suggested that His354 and His358 catalyze the formation of the oxetane intermediate that precedes light-initiated DNA repair. At pH 9.5 where the enzyme repair activity is highest His358 is deprotonated, whereas His354 is protonated, acting as the proton donor that initiates oxetane formation from the (6-4) photoproduct	Xenopus laevis	?	-	?

Synonyms

Synonyms	Comment	Organism
(6-4) photolyase	-	Xenopus laevis

pH Optimum

pH Optimum Minimum	pH Optimum Maximum	Comment	Organism
9.5	-	-	Xenopus laevis

pH Range

pH Minimum	pH Maximum	Comment	Organism
6	9.5	-	Xenopus laevis

Cofactor

Cofactor	Comment	Organism	Structure
FAD	-	Xenopus laevis

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Release 2023.1 (January 2023)