Table I. Chemical and enzymatic damage reactions of B vitamins and the corresponding cofactors.

Vitamin/Cofactor	Reactions	C/Ea	Referencesb
Thiamin (vitamin B1)/thiamin diphosphate	Pyrimidine ring deamination	C	Windheuser and Higuchi (1962)
	Thiazole ring oxidation	C,E	Bunik et al. (2007); Dwivedi and Arnold (1973)
	Thiazole ring breakdown	C	Jenkins et al. (2007)
	Oxidation to thiamin acetate	E	Dalvi et al. (1974)
	Hydrolysis to thiazole + pyrimidine	E	Jurgenson et al. (2009)
	Dephosphorylation	E	Rapala-Kozik et al. (2009)
	Thiamin triphosphate formation	E	Linster et al. (2013)
Riboflavin (vitamin B2)/FMN, FAD	(Photo)oxidative flavin ring loss	C	Choe et al. (2005)
	(Di)phosphate bond hydrolysis	E	Ogawa et al. (2008); Rawat et al. (2011)
	7α- and 8α-hydroxylation	E	Ohkawa et al. (1983)
	Cyclic FMN formation from FAD	C,E	Pinto et al. (1999); Sánchez-Moreno et al. (2009)
Niacin (vitamin B3)/NAD(P)(H)	Hydration of nicotinamide ring	C,E	Marbaix et al., (2011)
	Epimerization of β- to α-NAD(P)H	C	Oppenheimer and Kaplan (1975)
	Hydrolytic loss of nicotinamide ring	E	Everse et al. (1975)
	Diphosphate bond hydrolysis	E	Ogawa et al. (2008)
	Nicotinamide ring addition reactions	C	Everse et al. (1971)
Pantothenate (vitamin B5)/coenzyme A, ACPc	Oxidations of the thiol group	C	Huang et al. (2016)
	Diphosphate bond hydrolysis	E	Ogawa et al. (2008)
	Hydrolysis of the 3′ phosphate group	E	Paizs et al. (2008)
Pyridoxine (vitamin B6)/pyridoxal 5′-phosphate	Aldehyde group oxidation	C/E	Gerdes et al. (2012)
	Aldehyde group condensations	C	Dalling et al. (1976)
	Dephosphorylation	E	Gerdes et al. (2012)
	6-Hydroxylation	C	Tadera et al. (1986)
Biotin (vitamin B8)/biotinylated enzymes	Oxidation to biotin sulfoxide	C	Melville (1954)
	Side chain β-oxidation	E	Izumi et al. (1973)
Tetrahydrofolate/C1-substituted folates	Oxidative cleavage of C9-N10 bond	C	Gregory (1989)
	Pteridine ring oxidation	C/E	Noiriel et al. (2007)
	5-Formyltetrahydrofolate formation	C/E	Baggott (2000); Goyer et al. (2005)
	γ-Glutamyl bond hydrolysis	E	Orsomando et al. (2005); Bozzo et al. (2008)

^aC, chemical (i.e. nonenzymatic, spontaneous) reaction; E, enzymatic reaction or side-reaction.

^bCertain reactions have so far been reported only from animals or microbes.

^cACP, acyl carrier protein, which has a bound 4'-phosphopantetheinyl prosthetic group derived from coenzyme A.