title: Pepsin D. A minor component of commercial pepsin preparations.
abstract: Methods are described for the isolation and purification of pepsin D, an enzyme which accounts for about 10% of the enzymic activity in commercial preparations of pepsin. Pepsin D is similar to pepsin in having a molecular weight of about 35000, the same C-terminal amino acid sequence, and an N-terminal isoleucine residue. It differs in having no phosphate residue. Pepsin D is similar to pepsin in its ability to digest haemoglobin, acetyl-l-phenylalanyl-l-di-iodotyrosine and gelatin but it is twice as active as pepsin in the clotting of milk. It has the same specificity as pepsin in its action on the B-chain of oxidized insulin. It is probable that the pepsin D in commercial preparations of pepsin arises from the activation of gastric pepsinogen D.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002852:Chromatography, Ion Exchange; D004586:Electrophoresis; D004792:Enzyme Precursors; D005780:Gelatin / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008892:Milk / Q000187:drug effects; D008970:Molecular Weight; D010434:Pepsin A / Q000032:analysis*
chemical_list: D004792:Enzyme Precursors; D006454:Hemoglobins; D005780:Gelatin; D010434:Pepsin A