Studies with partially purified extracts of the nicotinamide adenine dinucleotide-linked l(+)-lactate dehydrogenase of Streptococcus cremoris US3 showed that fructose-1,6-diphosphate (FDP) was essential for the catalytic reduction of pyruvate in the pH range 5.0 to 7.0, outside of which the organism does not grow. In the absence of FDP, enzyme activity was observed only in the region of pH 8.0....

Whey, a byproduct of the cheesemaking process, is concentrated by processors to make whey protein concentrates (WPC) and isolates (WPI). Only 50% of whey proteins are used in foods. In order to increase their usage, texturizing WPC, WPI, and whey albumin is proposed to create ingredients with new functionality. Extrusion processing texturizes globular proteins by shearing and stretching them in...

To test the validity of thermodynamic parameters from the equilibrium method, we have studied the reversible heat-induced denaturations of lysozyme, ribonuclease A, cytochrome c and myoglobin at various pH values, using absorption spectral measurements. For each protein, if a linear temperature-dependence of the pre- and post-transition baselines is assumed for the analysis of the conformationa...

Abstract The current interest in individualized food through additive manufacturing has identified a need for more information on the formulation and printability of potential ingredients. Here, effect parameters casein–whey protein suspensions like pH (4.8–5.4) as well casein content (8.0–12.0% (w/w)) mixed with whey (2.0–3.0% pre-processing including denaturation proteins (80 °C, 10 min; adju...

The kinetics of the thermal inactivation of recombinant wild-type formate dehydrogenase from Candida boidinii yeast was studied in the temperature range of 53-61(o)C and pH 6.0, 7.0, and 8.0. It was shown that the loss of the enzyme's activity proceeds via a monomolecular mechanism. Activation parameters ∆Н(-) and ∆S(-) were calculated based on the temperature relations dependence of inactiva...

Escherichia coli adenylate kinase has a very well resolved proton nuclear magnetic resonance spectrum in the region containing signals from aromatic amino acid side-chains. We found that the protein is structurally stable over a wide pH range and renatures spontaneously after acidic as well as basic denaturation. Only one out of the three histidyl imidazole rings titrates on changing the pH and...

A procedure for extracting plasmid DNA from bacterial cells is described. The method is simple enough to permit the analysis by gel electrophoresis of 100 or more clones per day yet yields plasmid DNA which is pure enough to be digestible by restriction enzymes. The principle of the method is selective alkaline denaturation of high molecular weight chromosomal DNA while covalently closed circul...

Protein stability is measured by denaturation: When solvent conditions are changed (e.g., temperature, denaturant concentration, or pH) the protein population switches between thermodynamic states. The resulting denaturation curves have baselines. If the baselines are steep, nonlinear, or incomplete, it becomes difficult to characterize protein denaturation. Baselines arise because the chromoph...

The stability of four hemoglobins (Hb) in dimer forms (low concentration) were investigated by the kinetics of denaturation. The rate constants of denaturation were obtained by variation of 280 nm absorption versus time in 10 mM Tris-HCl, 10 mM EDTA, pH 8.0 at 45 degrees C in the absence and presence of 0.5 M ethanol, dimethyl sulfoxide (DMSO), formamide, and glycerol. The results show the tren...

In order to clarify the impact of Ca-binding sites (Ca1 and 2) on the conformational stability of neutral proteases (NPs), we have analyzed the thermal, pH and organic solvent stability of a NP variant, V189P/A195E/G203D/A268E (Q-mutant), from Salinovibrio proteolyticus. This mutant has shown to bind calcium more tightly than the wild-type (WT) at Ca1 and to possess Ca2. Q-mutant was resisted a...