Studies on the soluble and membrane-bound amino acid 2-naphthylamidases in pig and human epidermis
- 1 March 1977
- journal article
- research article
- Published by Portland Press Ltd. in Biochemical Journal
- Vol. 161 (3), 667-675
- https://doi.org/10.1042/bj1610667
Abstract
Membrane-bound (particulate) and soluble amino acid 2-naphthylamidases (EC 3.5.1.-) were present in subcellular fractions of epidermis from pig and human. The particulate enzymes exhibited Michaelis-Menten kinetics, with Km 5.1 .times. 10-5 (pig) and Km 7.3 .times. 10-5M (human) for the substrate L-leucine 2-naphthylamide. They were inhibited by puromycin and partially inhibited by EDTA. They did not require heavy metals and were not inhibited by thiol-group-blocking agents. Their pH optima were 7.0 (human) and 6.6 (pig). The particulate enzyme from pig epidermis retained 50% activity after 30 min at 70.degree. C. The soluble amino acid 2-naphthylamidases gave sigmoidal curves for reaction velocity vs. substrate concentration, and the kinetic data suggested that there was positive co-operativity between binding sites. This co-operativity was lost after treatment with 0.1 mM-p-hydroxymercuribenzoate and the enzymes showed 1st-order kinetics at low substrate concentrations. The soluble enzymes were inhibited by puromycin and by thiol-group-blocking agents and activated by dithiothreitol. They were inactivated above 60.degree. C and lost activity on storage, but this could be restored with dithiothreitol. The amino acid 2-naphthylamidases of human epidermis were much more active (2.5 times) towards L-alanine 2-napthylamide than towards the commonly used substrate L-leucine 2-naphthylamide. The kinetics of both the soluble and particulate enzymes from epidermis of some elderly patients with either diabetes or ischemia showed some differences from the kinetics of enzymes from healthy epidermis from younger individuals.This publication has 22 references indexed in Scilit:
- Lipid compositions of cells isolated from pig, human, and rat epidermis.Journal of Lipid Research, 1975
- Mitochondria and Nuclei of Pig and Human Epidermis: Isolation and Lipid CompositionJournal of Investigative Dermatology, 1975
- Studies on guinea pig skin cell cultures. 3. Minimum cell numbers for establishmentActa Dermato-Venereologica, 1974
- Error Theory and Ageing in Human Diploid FibroblastsNature, 1972
- Altered Enzymes in Ageing Human FibroblastsNature, 1972
- The lipid composition of rat-liver plasma membranesBiochimica et Biophysica Acta (BBA) - Biomembranes, 1968
- Studies on aminopeptidases in human bloodArchives of Biochemistry and Biophysics, 1963
- STUDIES ON DIPEPTIDASES AND AMINOPEPTIDASES .1. DISTINCTION BETWEEN LEUCINE AMINOPEPTIDASE AND ENZYMES THAT HYDROLYZE L-LEUCYL-BETA-NAPHTHYLAMIDE1963
- Histology and Cytochemistry of Human SkinJournal of Investigative Dermatology, 1961
- PROTEIN MEASUREMENT WITH THE FOLIN PHENOL REAGENTJournal of Biological Chemistry, 1951