Erythrina caffra trypsin inhibitor retains its native structure and function after reducing its disulfide bonds.

Erythrina trypsin inhibitor (ETI) from the seeds of Erythrina caffra is a high-affinity inhibitor of trypsin, chymotrypsin and tissue plasminogen activator. Its 172 amino acid polypeptide chain is stabilized in its compact, native state by two disulfide bonds. In spite of their conservation in all trypsin inhibitors of the soybean trypsin inhibitor (STI-Kunitz) family, their state of oxidation is essential only for protein stability but not for inhibitory function.

Topographical and enzymatic characterization of amylases from the extremely thermophilic eubacterium Thermotoga maritima.

The hyperthermophilic eubacterium Thermotoga maritima uses starch as a substrate, without releasing amylase activity into the culture medium. The enzyme is associated with the 'toga'. Its expression level is too low to allow the isolation of the pure enzyme.

Extremely thermostable D-glyceraldehyde-3-phosphate dehydrogenase from the eubacterium Thermotoga maritima.

D-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Thermotoga maritima, a hyperthermophilic eubacterium, has been isolated in pure crystalline form. The enzyme is a homotetramer with a subunit molecular mass of 37 kDa. The sedimentation coefficient of the native enzyme is 7.

Lactate dehydrogenase from the extreme halophilic archaebacterium Halobacterium marismortui.

D-Lactate dehydrogenase from the extreme halophilic archaebacterium Halobacterium marismortui has been partially purified by ammonium-sulfate fractionation, hydrophobic and ion exchange chromatography. Catalytic activity of the enzyme requires salt concentrations beyond 1M NaCl: optimum conditions are 4M NaCl or KCl, pH 6-8, 50 degrees C. Michaelis constants for NADH and pyruvate under optimum conditions of enzymatic activity are 0.

Lactate dehydrogenase from the extreme thermophile Thermotoga maritima.

Lactate dehydrogenase was isolated from the extreme thermophilic eubacterium Thermotoga maritima. The enzyme is stereospecific for L(+)-lactate. It represents a homotetramer of 144 kDa molecular mass, with a sedimentation coefficient of s20,w approximately 7 S.

Catalytic properties of thermophilic lactate dehydrogenase and halophilic malate dehydrogenase at high temperature and low water activity.

Thermophilic lactate dehydrogenases from Thermotoga maritima and Bacillus stearothermophilus are stable up to temperature limits close to the optimum growth temperature of their parent organisms. Their catalytic properties are anomalous in that Km shows a drastic increase with increasing temperature. At low temperatures, the effect levels off.

Folding mechanism of porcine ribonuclease.

The kinetics of unfolding and refolding of porcine ribonuclease were investigated. The unfolded state of this protein was found to consist of a fast-refolding species (UF) and two slow-refolding species (UIS and UIIS). After the rapid collapse of the structure during the N (native)----UF unfolding reaction, UIS and UIIS are produced from UF by two independent slow isomerizations of the unfolded polypeptide chain, leading ultimately to a mixture of about 10% UF, 20% UIIS and 70% UIS molecules at equilibrium.

Folding kinetics of mammalian ribonucleases.

The folding kinetics of seven different pancreatic ribonucleases are compared both under native conditions and within the unfolding transition. In general, the folding kinetics of these proteins are similar despite numerous amino acid substitutions. Ribonucleases with 4-6 proline residues show 80% slow-folding species.

Role of proline peptide bond isomerization in unfolding and refolding of ribonuclease.

The isomerization of the proline peptide bond between tyrosine-92 and proline-93 in bovine pancreatic ribonuclease A has been investigated in the unfolded protein as well as during the slow refolding process. This bond is in the cis state in the native protein. By comparison of various homologous ribonucleases we show that isomerization of proline-93 is associated with a change in fluorescence of tyrosine-92.