FIG. 1.

Hexokinase activity in extracts from wild-type M. xanthus cells is a linear function of protein concentration. Activities of hexokinase are plotted as a function of total protein in extracts prepared from wild-type M. xanthus cells, are the averages of three determinations, and had standard deviations of <±0.032 nmol min⁻¹. Extracts were incubated in 50 mM Tris–10 mM MgCl₂ (pH 9.1) with 500 to 1,000 U of Glc6P dehydrogenase plus Glc (20 mM) and ATP (10 mM) (filled circles), ATP (10 mM) (open circles), or Glc (20 mM) (squares). The observed rates of NADP reduction in the absence of added ATP (squares) are similar in reactions with or without added extract, activity is dependent on the addition of Glc, and the addition of Glc decreases the rate of spontaneous NADP reduction in the complete assay without added extract.