New Insights into the Proteolytic System of Streptococcus thermophilus: Use of Isracidin To Characterize Cell-Associated Extracellular Peptidase Activities

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• 作者：Zeeshan Hafeez ; C茅line Cakir-Kiefer ; Jean-Michel Girardet ; Xavier Lecomte ; C茅dric Paris ; Wessam Galia ; Annie Dary ; Laurent Miclo
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2015
• 出版时间：September 2, 2015
• 年：2015
• 卷：63
• 期：34
• 页码：7522-7531
• 全文大小：375K
• ISSN：1520-5118

文摘

The influence on the hydrolysis of isracidin of cell-associated extracellular aminopeptidase and X-prolyl dipeptidyl peptidase activities in addition to protease PrtS of Streptococcus thermophilus strains was investigated. S. thermophilus LMD-9 (PrtS⁺ phenotype) efficiently hydrolyzed the isracidin mainly through the PrtS activity, whereas strain CNRZ1066 (PrtS^{鈥?/sup> phenotype) and two mutant strains LMD-9-螖prtS and LMD-9-螖prtS-螖htrA also displayed substrate hydrolysis, but different from that of the wild type strain LMD-9. Identification by mass spectrometry of breakdown products of isracidin revealed the existence of novel cell-associated extracellular carboxypeptidase and peptidyl dipeptidase activities in all PrtS鈥?/sup> strains, besides known cell-associated extracellular aminopeptidase and X-prolyl dipeptidyl peptidase activities. Both aminopeptidase and peptidyl dipeptidase activities were not able to cleave the isracidin at peptide bonds with proline residues. No hydrolysis of isracidin was detected in cell free filtrate for all the strains studied, indicating that no cell lysis had occurred. Taken together, these results suggested the presence of cell-associated extracellular peptidase activities in S. thermophilus strains that could be vital for the growth of PrtS鈥?/sup> strains.}