TABLE 1.

Specific activity of DHPR from T. thermophilus with various substrates^a

Substrate	Sp act (U/mg of protein)
6-Biopteridin	<0.05
PtH2	<0.05
qPtH2	26.2 ± 2.7
Potassium ferricyanide	<0.05
FH2	5.2 ± 1.1

^aActivity was measured at 35°C in 50 mM potassium phosphate buffer (pH 7.5) in the presence of 0.1 mM NADPH and 0.1 mM pteridine.