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Exam Review - Chapter 18

Chymotrypsinogen procarboxypeptidases a and b

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Unformatted text preview: pepsinogen, the inactive form of pepsin o Pepsin is created by autocatalytic cleavage that occurs at a low pH o Low pH triggers secretion of secretin, which stimulates the pancreas to secrete bicarbonate and neutralize the acidity of the HCl o Cholecystokinin: stimulates the secretion of several pancreatic enzymes such as trypsinogen, chymotrypsinogen, procarboxypeptidases A and B Trypsinogen is converted to its active form by enteropeptidase • Activates chymotrypsinogen, procarboxypeptidases, and proelastase o Carboxypeptidases remove carboxyl- terminal residues from peptides o Aminopeptidases: remove amino- terminal residues from short peptides Removal of the α- amino groups is the first step of amino acid catabolism o Promoted by enzymes aminotransferases or transaminases o Amino group is removed from amino acid and transferred to α- ketoglutarate All aminotransferases have same prosthetic group and same reaction mechanism o Pyridoxal phosphate: the prosthetic group Functions as an intermediate carrier of amino groups • Can accept and donate amino groups Participates in a variety of reactions at the α, β, and γ carbons of amin acids • Reactions at the α- carbon include racemizations, decarboxylations, and transaminations Pr...
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