Acid protease from stomach of vertebrates. Cleaves preferentially between two hydrophobic amino acids (e.g. F L, F Y) and will attack most proteins except protamines, keratin and highly glycosylated proteins. A single chain phosphoprotein (327 amino acids, 34.5 kD) released from the enzymatically inactive zymogen, pepsinogen, by autocatalysis at acid pH in the presence of HCl. One of the peptides cleaved off in this process is a pepsin inhibitor and has to be further degraded to allow the pepsin to have full activity.
This entry appears with permission from the Dictionary of Cell and Molecular Biology
(11 Mar 2008)
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