TABLE 2.

Comparison of enzyme activities of different molybdoenzymes in R. capsulatus moeA mutant strain R507 and the parental strain KS36

Strain	Relevant genotype	Enzyme activity (U/mg)a
		Xanthine dehydrogenaseb		Nitrate reductasec		DMSO reductased
		1 μM Mo	1 mM Mo	1 μM Mo	1 mM Mo	1 μM Mo	1 mM Mo
KS36	ΔnifHDK	0.0067	0.0071	0.14	0.14	0.085	0.22
R507	ΔnifHDK moeA	—e	0.0059	—	—	—	—

^aEnzyme activities were analyzed in crude extracts after photoheterotrophic growth on RCV medium containing 10 mM ammonium (xanthine dehydrogenase), 10 mM ammonium plus 0.1% nitrate (nitrate reductase) or 10 mM ammonium plus 30 mM DMSO (DMSO reductase). Mean values were calculated from at least six independent measurements. 

^bXanthine dehydrogenase activity is expressed as micromoles of NAD reduced per minute per milligram of protein. 

^cNitrate reductase activity is expressed as micromoles of nitrate reduced per minute per milligram of protein. Genes for nitrate reductase from R. sphaeroides were introduced into the corresponding R. capsulatus strains on a replicative plasmid (31). 

^dDMSO reductase activity is expressed as micromoles of DMSO reduced per minute per milligram of protein. 

^e—, below the limit of detection.