Purification and Properties of d‐Glyceraldehyde‐3‐Phosphate Dehydrogenase from an Extreme Thermophile, Thermus thermophilus Strain HB 8

Abstract

1 d‐Glyceraldehyde‐3‐phosphate dehydrogenase from an extreme thermophile, T. thermophilus strain HB8, was purified and crystallized. 2 The enzyme was found to possess remarkable heat stability, being slowly inactivated at 900C. 3 Basic kinetic constants and pH profile are reported. The enzyme was activated 25‐fold by 90 mM NH₄CI, and also by ethanol up to 5‐fold at 30 °C. 4 The enzyme was found to be far more resistant to urea or sodium dodecylsulfate than the rabbit enzyme. 5 The enzyme was shown to be a tetramer of molecular weight 130000‐ 135000. Amino acid composition analysis revealed no unusual features. Circular dichroic spectra suggested that the contents of the ordered structure of the thermophile enzyme are similar to those of the rabbit enzyme. 6 The other catalytic properties of the thermophile enzyme are discussed in comparison with those of the enzymes from other sources.