STABILITY OF GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASES FROM HYPERTHERMOPHILIC ARCHAEA AT HIGH-TEMPERATURE

Resistance of the primary structure towards heat-induced irreversible damages represents one of the most important prerequisites for a stabl e protein structure at the growth temperature of hyperthermophiles. An alyses with glyceraldehyde-3-phosphate dehydrogenases from Methothermu s fervidus and Pyrococcus woesei indicate a correlation between heat r esistance of the peptide chain and conformation stability. Irreversibl e heat injuries of the peptide chain proceed preferrently in unfolded proteins but are retarded in the folded state. Consequently, extrinsic factors stabilizing the native protein conformation also protect the peptide chain. Thus, in the case of the enzymes from M. fervidus and P . woesei high phosphate concentrations stabilize the protein conformat ion and accordingly the peptide chain towards deamidation of Asn resid ues and hydrolysis of the peptide bond, although the chemical modifica tion reaction itself is favoured at high ionic strength.