D-glyceraldehyde-3-phosphate dehydrogenase. The purification and characterisation of the enzyme from the thermophiles Bacillus stearothermophilus and Thermus aquaticus.

1. D-Glyceraldehyde-3-phosphate dehydrogenase from two thermophilic bacteria has been purified by procedures including affinity chromatography on NAD+-Sepharose. 2. Methods for making NAD+-free enzyme are also described. 3. Both the holo and apo forms of the enzyme from Bacillus stearothermophilus have been crystallised. 4. The enzymes are tetrameric and composed of four chemically identical polypeptide chains of molecular weight 36,000. 5. The enzymes are much more stable to heat than their counterparts from mesophiles.