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Protease Activities in Raw Milk Determined Using a Synthetic Heptapeptide Substrate
Author(s) -
O'Driscoll B. M.,
Rattray F. P.,
McSweeney P. L. H.,
Kelly A. L.
Publication year - 1999
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1999.tb15094.x
Subject(s) - chemistry , substrate (aquarium) , protease , peptide , hydrolysis , cysteine , chromatography , cysteine protease , biochemistry , enzyme , cathepsin , hydrolysate , incubation , cathepsin b , proteases , biology , ecology
A synthetic heptapeptide (H‐Pro‐Thr‐Glu‐Phe‐[p‐nitro‐Phe]‐Arg‐Leu‐OH) was used as substrate for detection and assay of cathepsin D in raw bovine milk. Cathepsin D produced a specific peptide, as detected by HPLC analysis of peaks for product and substrate. On incubation of acid wheys from milk samples with the substrate, three hydrolysis products were detected and bonds cleaved were identified by mass spectrometry. Inhibition studies were performed to identify enzymes responsible for the hydrolysis. One activity was cathepsin D and production of another peptide was inhibited by cysteine protease inhibitors, suggesting cysteine protease activity in milk.