... aldehyde concen-tration was determined using the DXR assay.1H-NMR(500 MHz, D 2O, 1 : 2 mixture of the aldehyde and of thehydrate): d ¼ 0.93 (2H, s, CH3,hydrate);1.10(1H,s,CH3,aldehyde);3.62(2H,m,2· ... AHIR, acetohydroxy acid isomeroreductase;H2-NADPH, dihydro-NADPH; DXP, 1-deoxy- D -xylulose5-phosphate; DXR, 1-deoxy- D -xylulose 5-phosphate reducto-isomerase; DXS, 1-deoxy- D -xylulose ... by the condensation of(hydroxyethyl)thiamine resulting from pyruvate 1 decarb-oxylation on glyceraldehyde 3-phosphate 2 catalyzed bythe thiamine diphosphate-dependent DXP synthase (DXS)[4–6]....