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Changes in NAD(P) + ‐dependent malic enzyme and malate dehydrogenase activities during fibroblast proliferation
Author(s) -
McKeehan Wallace L.,
McKeehan Kerstin A.
Publication year - 1982
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041100206
Subject(s) - malic enzyme , malate dehydrogenase , nad+ kinase , biochemistry , dehydrogenase , citric acid cycle , cytosol , enzyme , glycerol 3 phosphate dehydrogenase , biology , pyruvate dehydrogenase complex , chemistry
A sensitive isotope exchange method was developed to assess the requirements for and compartmentation of pyruvate and oxalacetate production from malate in proliferating and nonproliferating human fibroblasts. Malatedependent pyruvate production (malic enzyme activity) in the particulate fraction containing the mitochondria was dependent on either NAD + or NADP + . The production of pyruvate from malate in the soluble, cytosolic fraction was strictly dependent on NADP + . Oxalacetate production from malate (malate dehydrogenase, EC 1.1.1.37) in both the particulate and soluble fraction was strictly dependent on NAD + . Relative to nonproliferating cells, NAD + ‐linked malic enzyme activity was slightly reduced and the NADP + ‐linked activity was unchanged in the particulate fraction of serum‐stimulated, exponentially proliferating cells. However, a reduced activity of particulate malate dehydrogenase resulted in a two‐fold increase in the ratio of NAD(P) + ‐linked malic enzyme to NAD + ‐linked malate dehydrogenase activity in the particulate fraction of proliferating fibroblasts. An increase in soluble NADP + ‐dependent malic enzyme activity and a decrease in NAD + ‐linked malate dehydrogenase indictated an increase in the ratio of pyruvate‐producing to oxalacetate‐producing malate oxidase activity in the cytosol of proliterating cells. These coordinate changes may affect the relative amount of malate that is oxidized to oxalacetate and pyruvate in proliferating cells and, therefore, the efficient utilization of glutamine as a respiratory fuel during cell proliferation.