ABSTRACT
Proteolysis of recombinant human proinsulin by the native trypsin, by trypsin modified with a copolymer of vinylpyrrolidone and acrolein, and by the same modified trypsin immobilized on Silochrom 1.5 was studied by RP HPLC and mass spectrometry. Rate constants of the main stages of proinsulin hydrolysis by the native trypsin were estimated. The values of rate constants of the digestions of the most easily hydrolyzable bonds (those formed by the pairs of the basic amino acid residues) in proinsulin were found to be of the same order as those formed by the separate lysine residues (Lys7) and those formed by the four basic amino acid residues of the C-terminal cluster of melittin. It was established that covalent trypsin binding to the copolymer did not change the ratio of the rate constants of the individual stages of proinsulin hydrolysis, whereas after the immobilization of modified trypsin on the Silochrome, the formation of diarginyl insulin-ArgArg, intermediate forms of hydrolyzed insulin, and desThr-insulin proceeds with comparable rates.
Subject(s)
Enzymes, Immobilized/chemistry , Proinsulin/chemistry , Trypsin/chemistry , Amino Acid Sequence , Chromatography, High Pressure Liquid , Humans , Hydrolysis , Kinetics , Molecular Sequence Data , Recombinant Proteins/chemistry , Spectrometry, Mass, Matrix-Assisted Laser Desorption-IonizationABSTRACT
Hydrolysis of the C-peptide from recombinant human proinsulin, porcine insulin, and melittin by the E. coli actin-degrading proteinase ECP 32 was studied by reverse phase high performance liquid chromatography and mass spectrometry with electrospray ion source. Proteinase ECP 32 hydrolyzed only melittin at the Ala15-Leu16 or Leu16-Ile17 bonds (KM = 2.4 x 10(-6) M). The effects of pH and buffer composition on the rate of enzymatic hydrolysis were studied. The pH optimum of melittin hydrolysis was 7. Phosphates inhibited, whereas ATP stimulated the hydrolysis of melittin. Melittin was suggested as a substrate for determining the activity of proteinase ECP 32.
