Preparation and activation of a spin-labeled pepsinogen. Biochemistry 1981 Mar 03;20(5):1267-72
Date
03/03/1981Pubmed ID
6261787DOI
10.1021/bi00508a034Scopus ID
2-s2.0-0019871856 (requires institutional sign-in at Scopus site) 15 CitationsAbstract
gen derivative has been prepared, using 3-[[2,5-dioxo-1-pyrrolidinyl)oxy]carbonyl]-2,5-dihydro-2,2,5,5-tetramethyl-1H-pyrrolyl-1-oxy with 3 spin-labels/protein molecule. Two are located in the peptide that is released first (1-16) and the other is in the secondarily removed sequence (17-44). Activation of the labeled zymogen is a faithful model of native pepsinogen activation because the two processes are closely related in rate, pH dependence of rate, and sites of peptide bond cleavage. The ESR signal associated with the bound label changes during activation due to release of the activation peptide. The rate of release (0.5 min(-1) at pH 2, 22 degrees C) is an order of magnitude slower than is the rate of activation, i.e., cleavage of the peptide bond that holds the peptide to the enzyme. Activation in the presence of pepstatin, however, results in peptide release (2 min(-1) at pH 2, 22 degrees C) nearly as fast as activation occurs. At pH values between 2.5 and 3, there is a lag in the change of the ESR signal following acidification. This indicates accumulation of an intermediate with pH 8.5 labile activity that still has its activation peptide attached. The strong temperature dependence of the rate of activation (26 kcal/mol) is reflected neither in reported characteristics of pepsin catalysis nor in the measured rate of release of the activation peptide from the enzyme (13 kcal/mol).
Author List
Twining SS, Sealy RC, Glick DMAuthor
Sally S. Twining PhD Assistant Dean, Professor in the Biochemistry department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsBinding Sites
Electron Spin Resonance Spectroscopy
Enzyme Activation
Kinetics
Pepsinogens
Peptide Fragments
Protein Binding
Spin Labels
Swine