. 2007 Nov 14;408(Pt 2):149–159. doi: 10.1042/BJ20070677

Table 2. Enzymatic activity of maize THI3 protein: the rates of TMP formation from various combinations of substrates and cofactors.

Concentrations in the reaction mixture were 15 μM HMP, HMP-P, HMP-PP, HET-P or HET, 10 mM ATP and 10 mM MgCl₂. Samples containing 5 μg of protein/100 μl in 50 mM Tris/HCl buffer (pH 8.0) were incubated for 60 min at 37 °C and then analysed for TMP content by RP-HPLC with fluorogenic post-column derivatization. Values are the means±S.D. from at least three independent kinetic experiments.

Activity tested	Substrates and cofactors	Specific activity (nmol of TMP/min per mg of protein)
TMP synthase	HMP-PP, HET-P	0.52±0.05
	HMP-PP, HET-P, Mg²⁺	2.46±0.12
	HMP-PP, HET-P, ATP	0.05±0.02
	HMP-PP, HET-P, Mg²⁺, ATP	0.83±0.11
HMP kinase/TMP synthase	HMP, HET-P, ATP, Mg²⁺	0.22±0.03
HMP-P kinase/TMP synthase	HMP-P, HET-P, ATP, Mg²⁺	0.24±0.02
HET kinase/TMP synthase	HMP-PP, HET, ATP, Mg²⁺	0