title: Digestion of insulin derivatives with subtilisin: a kinetic study.
abstract: Native, denatured, performic acid-oxidized or S-sulfo insulin and S-sulfo or performic acid-oxidized A- and B-chains were digested with subtilisin type Carsberg. The proteolysis was followed by measuring the uptake of alkali through autotitration. The kinetic study shows the existence of 2 first-order reaction classes which differ markedly in rate constant. The number of bonds split with fast and with slow reactions has been calculated. Only one of a total of 12 cleavable bonds in native insulin is opened by fast reaction. In the denatured protein the number of bonds split by the fast reaction increases to 4 and in the oxidized and S-sulfo protein 3 bonds are cleaved, while the slow cleavable bonds number 2 and 7, respectively, The kinetic study of the proteolysis of S-sulfo A-chain and of oxidized or S-sulfo B-chain shows that two bonds are split in A-chain with the fast and slow reactions, while in B-chain only one of the six cleavable bonds is susceptible to fast attack.
mesh_terms: D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000031:analogs & derivatives* / Q000378:metabolism; D007700:Kinetics; D011489:Protein Denaturation; D013381:Subtilisins / Q000378:metabolism*; D013997:Time Factors
chemical_list: D007328:Insulin; D013381:Subtilisins