A kinetic model for hydrolysis of whey proteins by cardosin A extracted from Cynara cardunculus

• Type: Article in International Scientific Journal
• Date: 2004

Authors

Barros, RM (Author) Other; F. Xavier Malcata (Author) Other

Journal

Title: Food Chemistry

Vol. 88

Pages: 351-359

ISSN: 0308-8146

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 21 Citations

Scopus - 30 Citations

Other information

Authenticus ID: P-000-7FQ

DOI: 10.1016/j.foodchem.2004.01.046

Abstract (EN): The enzymatic hydrolysis of the major whey proteins, namely beta-lactoglobulin (beta-Lg) and alpha-lactalbumin (alpha-La), was experimentally studied using whey as substrate; an aspartic protease (cardosin A), previously extracted from the flowers of Cynara cardunculus and purified by gel filtration and ion exchange chromatographies, was used for this purpose. Sweet whey was incubated for 24 h at various enzyme: substrate ratios, at controlled pH (5.2 and 6.0) and temperature (55 degreesC); the hydrolyzates were assayed by gel permeation chromatography and electrophoresis. A mechanistic model was proposed for the kinetics, which basically leads to a double-substrate, single-enzyme Michaelis-Menten rate expression containing four adjustable parameters; these parameters were estimated by applying multiresponse, nonlinear regression analysis to the experimental data, so that the model would yield good fits. The best estimates obtained for K(m) were markedly lower for alpha-La than for beta-Lg, so cardosin A shows a higher affinity for alpha-La than for beta-Lg. The experimental results also suggest that beta-Lg is rather resistant to enzyme-mediated hydrolysis under all experimental conditions tested. The highest activity (measured by k(cat)) of cardosin A was recorded toward alpha-La (i.e. 0.013 s(-1)) at pH 5.2. Furthermore, the specificity ratio (k(cat)/K(m)), obtained toward each whey protein, indicated that cardosin A possesses a higher catalytic efficiency for hydrolysis of alpha-La than of beta-Lg; the highest value for this ratio was recorded for alpha-La at pH 5.2, and was close to that reported elsewhere for cardosin A acting on caseins and casein-like substrates.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9