Specificity of Carboxypeptidases from Actinomucor elegans and Their Debittering Effect on Soybean Protein Hydrolysates

Abstract

The specificities of carboxypeptidases from Actinomucor elegans were investigated by determining enzymatic activities at pH 7.0 and pH 4.0 with 16 Z-dipeptides and three Z-tripeptides as substrates. The debittering effect was evaluated and the free amino acid compositions of the soybean protein hydrolysates were analyzed before and after treatment with A. elegans extract at pH 7.0 and pH 4.0, with carboxypeptidases from Aspergillus oryzae as control. The results of the enzyme activity determinations indicated that carboxypeptidases from A. elegans prefer hydrophobic substrates, such as Z-Phe-Leu, Z-Phe-Tyr-Leu, and Z-Phe-Tyr. The sensory evaluation and free amino acid composition analysis showed that these carboxypeptidases are efficient tools for decreasing the bitterness of peptides because they liberated the fewest free amino acids, which consisted of 73% hydrophobic amino acids, under acidic conditions. Carboxypeptidases from A. elegans display promising prospects for future applications in the protein hydrolysate industry.

Effects of exopeptidase treatment on antihypertensive activity and taste attributes of enzymatic whey protein hydrolysates

“…Aminopeptidases and carboxypeptidases are two types of exopeptidases that cleave amino acid residues from the N-and C-terminal of peptides, respectively. Exopeptidase treatment can decrease hydrolysate bitterness by releasing hydrophobic amino acids from the N-terminal (Nishiwaki, Yoshimizu, Furuta, & Hayashi, 2002), C-terminal (Fu, Li, & Yang, 2011), or both terminals (Ge & Zhang, 1996). Although effective for debittering, however, hydrolysis with exopeptidases may result in cleaving off amino acid residues pertinent to ACE-inhibitory activity.…”

Characterization of a novel metallocarboxypeptidase from Streptomyces cinnamoneus TH-2

“…The result of catalytic efficiency of TH2-CP toward Z-Gly-Leu and Z-Gly-Gly-Leu may be due to the combined effect of affinity and reactivity toward the substrates. The activity of carboxypeptidase from Actinomucor elegans toward Z-Gly-Gly-Leu and Z-Gly-Phe was about 0.5 μmol/h/ ml at pH 7 and 37 °C (Fu et al 2011). In contrast, the activities of TH2-CP toward them were 60.3 ± 4.8 and 30.0 ± 1.1 μmol/h/ml at pH 7 and 40 °C, respectively (data not shown).…”

“…This finding indicates that TH2-CP can decrease the bitterness of peptides. It was confirmed that carboxypeptidases from wheat, pancreatin, and Actinomucor elegans (Fu et al 2011;Ge and Zhang 1996;Komai et al 2007;Umetsu et al 1983),which can effectively hydrolyze hydrophobic amino acids at the C-terminus, can decrease the bitterness of peptides, including the peptides produced by proteolytic digestion of casein. Thus, we consider that the metallocarboxypeptidase TH2-CP from S. cinnamoneus TH-2 could also be used to decrease the bitterness of peptides in food industry, since it has a good …”

“…Therefore, we used the phosphate buffer as the reaction buffer at pH 7 in the subsequent experiments. Unlike the carboxypeptidases from several genera of fungus, such as Aspergillus (Ichishima 1972), Penicillium (Yokoyama et al 1974), and Monascus (Liu et al 2004a, b), which have an optimum pH in the range from 3 to 5.2, the optimum pH of TH2-CP is close to that of the carboxypeptidase from Actinomucor elegans (Fu et al 2011), which has an optimum pH of approximately 7. The optimum temperature for TH2-CP activity was 51 °C (Fig.…”

“…They function in a variety of physiological processes such as fibrinolysis, inflammation, blood coagulation, and prohormone and neuropeptide processing (Arolas et al 2007;Vendrell et al 2000). They can also be used to decrease the bitterness of peptides in food industries (Fu et al 2011;Ge and Zhang 1996;Komai et al 2007;Umetsu et al 1983). According to the presence of particular active site residues, carboxypeptidases are classified as metallocarboxypeptidases, serine carboxypeptidases, or cysteine carboxypeptidases.…”