Table 1. Mutations introduced in hydrogenases resulting in positive effects on hydrogen production or tolerance to dioxygen (see the text for details).

Enzyme, organism	Mutation	Main effect	Ref.
HoxG (MBH), [NiFe] R. eutropha	C81A, C81V, C81S, C81T (catalytic subunit)	Higher (variable) O2 tolerance	98
Periplasmic, [NiFe] D. fructosovorans	V74M, V74C, V74S, V74N (catalytic subunit)	Increased O2 tolerance, decreased H2 oxidation	33,99,100
HycG (hydrogenase-3), [NiFe] K. oxytoca	G47C, G50C, G113C, G120C, G50C/G120C (ET subunit)	Increased O2 tolerance, unaltered in vivo activity	107
HydA1, [FeFe] Ch. reinhardtii	R171D (catalytic unit)	Decreased H2 evolution but increased Vmax	78
HycE (hydrogenase-3), [NiFe] E. coli	Various, random (catalytic unit)	Increased H2 production	79
Periplasmic, [NiFe] D. fructosovorans	P238C (ET subunit)	Shift in catalytic bias towards H2 production	84
HynS, [NiFe] A. macleodii	P285C/H230C (ET subunit)	Shift in catalytic bias towards H2 production	85
HupS, uptake, [NiFe] N. punctiforme	C12P (ET subunit)	Shift in catalytic bias towards H2 production in vivo	87
HyaA (MBH/hydrogenase-1), [NiFe] E. coli	E73Q (ET subunit)	Shift in catalytic bias towards H2 production	88