Erepsin is a protein fraction found in the intestinal juices and contains a group of enzymes that digest peptones into amino acids. It is produced and secreted by the intestinal glands in the ileum and the pancreas. It is also found widely in other cells.
Erepsin was discovered at the beginning of the twentieth century by German physiologist Otto Cohnheim (1873-1953) who found a substance that breaks down peptones into amino acid in the intestines. He termed this hypothetical protease in his protein extract "erepsin", derived from a Greek word meaning "I break down" (έρείπω). His discovery was significant as it overturned the previous "hypothesis of resynthesis" which proposed that proteins were broken down into peptones from which proteins were then resynthesized, and helped establish the idea of free amino acids instead of peptones as the building blocks of protein.
Later, it was found that erepsin is a complex mixture of different peptidases. It was also found not to be unique to intestinal mucosa and is present in other cells. The term erepsin however had gradually fallen from use in scientific literature in the latter half of the twentieth century as more precise terms were preferred, and may be now considered obsolete.
Erepsin may contain dipeptidases, aminopeptidases and occasionally carboxypeptidases, and is often grouped under exopeptidases, proteases that work only on the outermost peptide bonds of a polypeptide chain. The optimum pH is around pH 8.
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