pubmed.ncbi.nlm.nih.gov

The pH-dependence of pepsin-catalysed reactions - PubMed

The pH-dependence of pepsin-catalysed reactions

A J Cornish-Bowden et al. Biochem J. 1969 Jun.

Abstract

1. The pH-dependence of the pepsin-catalysed hydrolysis of three peptide substrates was studied by using a method for the continuous monitoring of the formation of ninhydrin-positive products. 2. Two peptide acid substrates, N-acetyl-l-phenylalanyl-l-phenylalanine and N-acetyl-l-phenylalanyl-l-phenylalanyl-glycine, show apparent pK(a) values of 1.1 and 3.5 in the plots of k(0)/K(m) versus pH. By contrast a neutral substrate, N-acetyl-l-phenylalanyl-l-phenylalanine amide, shows apparent pK(a) values of 1.0 and 4.7. 3. Together with the data of the preceding paper (Knowles, Sharp & Greenwell, 1969), these results are taken to indicate that the rate of pepsin-catalysed hydrolysis is controlled by the ionization of two groups, which on the free enzyme have apparent pK(a) values of 1.0 and 4.7. It is apparent that the anions of peptide acid substrates are not perceptibly bound to the enzyme, resulting in apparent pK(a) values of 3.5 for the dependence of k(0)/K(m) for these materials.

PubMed Disclaimer

Similar articles

Cited by

References

    1. J Biol Chem. 1965 Oct;240(10):3810-5 - PubMed
    1. Biochemistry. 1965 Aug;4(8):1537-43 - PubMed
    1. Biochem J. 1966 May;99(2):275-82 - PubMed
    1. J Biol Chem. 1966 Jun 10;241(11):2720-30 - PubMed
    1. Biochemistry. 1966 Jul;5(7):2473-83 - PubMed

MeSH terms

Substances