Abstract:Mitochondrial NAD(P)-dependent malic enzyme [EC 1.1.1.39, L-malate: NAD(+) oxidoreductase (decarboxylating)] was purified from herring skeletal muscle to a specific activity of 8.2 μmol/min/mg. The purification procedure involved chromatography on DEAE-cellulose, Red Agarose and a Sephacryl S-300 with a final recovery of 38% of enzyme activity. This enzyme catalyzes the oxidative decarboxylation of malate in the presence of either NAD or NADP in the presence of Mn(2+). Some kinetic characteristics of this enzy… Show more
“…Inhibition of NAD-preferring ME could be overcome by fumarate and in consequence could adjust spermatozoa metabolism to changing levels of ATP and fumarate (Niedźwiecka et al 2017). Previously, it has been shown that ATP is an effective inhibitor of both NAD- and NADP-linked reaction by NAD(P)-ME from mammals and fish (Sauer 1973; Lin and Davis 1974; Skorkowski and Storey 1988, 1990; Żołnierowicz et al 1988). Fig.…”
Herring (Clupea harengus) shows the unique behavior of reproductive biology in which spermatozoa remains in the surrounding media for extended periods. It is an excellent model for studying the malic enzyme (ME) and creatine kinase (CK) biochemical properties because of their high activity and variability of molecular isoforms. The specific activity of NAD-preferring ME in herring spermatozoa is the highest among other fish spermatozoa and is localized in its large mitochondrion. Two different CK isoforms, dimer and octamer, were detected in herring spermatozoa. It has already been shown that CK isoforms play an important role in energy homeostasis by catalyzing a reversible transfer of the phosphate of ATP to creatine to yield ADP and creatine phosphate (CP) (creatine/CP circuit). Two lactate dehydrogenase (LDH) isoenzymes were also shown in herring spermatozoa, LDH-B4 and LDH-A2B2. In this mini-review, the role of ME and energy transport system with easily diffusible creatine and CP in herring spermatozoa is discussed.
“…Inhibition of NAD-preferring ME could be overcome by fumarate and in consequence could adjust spermatozoa metabolism to changing levels of ATP and fumarate (Niedźwiecka et al 2017). Previously, it has been shown that ATP is an effective inhibitor of both NAD- and NADP-linked reaction by NAD(P)-ME from mammals and fish (Sauer 1973; Lin and Davis 1974; Skorkowski and Storey 1988, 1990; Żołnierowicz et al 1988). Fig.…”
Herring (Clupea harengus) shows the unique behavior of reproductive biology in which spermatozoa remains in the surrounding media for extended periods. It is an excellent model for studying the malic enzyme (ME) and creatine kinase (CK) biochemical properties because of their high activity and variability of molecular isoforms. The specific activity of NAD-preferring ME in herring spermatozoa is the highest among other fish spermatozoa and is localized in its large mitochondrion. Two different CK isoforms, dimer and octamer, were detected in herring spermatozoa. It has already been shown that CK isoforms play an important role in energy homeostasis by catalyzing a reversible transfer of the phosphate of ATP to creatine to yield ADP and creatine phosphate (CP) (creatine/CP circuit). Two lactate dehydrogenase (LDH) isoenzymes were also shown in herring spermatozoa, LDH-B4 and LDH-A2B2. In this mini-review, the role of ME and energy transport system with easily diffusible creatine and CP in herring spermatozoa is discussed.
Two malic enzymes are present in liver mitochondria from Squalus acanthias (spiny dogfish), a n NAD(P)-dependent and a n NADP-dependent malic enzyme. The NAD(P)-dependent enzyme was partially purified and found to have kinetic properties similar to other malic enzymes; the molecular weight is = 130,000. The maximal rate with NADP is 40% of the maximal rate with NAD. The NADP-dependent malic enzyme was purified to homogeneity and also has properties similar to other malic enzymes, including a subunit molecular weight of = 61,000 and a native molecular weight of -250,000; however, the rate as a function of malate concentration is described by a sigmoid curve. Both enzymes require either Mn2+ or M P for activity, are activated by fumarate or succinate, and are inhibited by ATP. Both enzymes a r e inhibited by low concentrations of oxalacetate; the Ki for competitive inhibition of the NAD(P)-dependent malic enzyme by oxalacetate is 4 pM. The K,,, for Mn2+ is considerably lower than the K,,, for Mg2' for both enzymes; the maximal rate with Mg2+ is about the same a s with Mn2+ for the NADPdependent enzyme, but only 20% of that with Mn2+ for the NAD(P)-dependent enzyme. The possible role of these enzymes in contributing to citrate synthesis by isolated spiny dogfish liver mitochondria is discussed. NAD-or NADP-dependent malic enzyme activity could not be detected in the cytosol. 0 1995 Wiley-Liss, Inc.
Mitochondrial NAD(P)-dependent malic enzyme [EC 1.1.1.39, L-malate: NAD(+) oxidoreductase (decarboxylating)] was purified from herring testicular tissue to a specific activity of 26.4 μmol NADH/min/mg protein. Herring testicular tissue is one of the most abundant sources of this enzyme. The purification procedure involved differential centrifugation of mitochondria and then chromatography on DEAE-Sephacel, Red Agarose and Sephacryl S-300. This enzyme catalyzes the oxidative decarboxylation of malate in the presence of Mn(2+) and either NAD or NADP. Under Vmax conditions the ratios for the rate of NAD/NADP reduction was 1.8. A study of the reductive carboxulation reaction indicated that this enzyme reaction is reversible; at pH 7.0 the reverse reaction exhibited 22% of the activity of forward reaction. Some kinetic characteristics of the enzyme were determined. ATP was found to be a competitive inhibitor with respect to malate. Fumarate reversed ATP inhibition. Regulation of NAD(P)-dependent malic enzyme from herring testicular tissue mitochondria could respond to changing levels of mitochondrial ATP and fumarate in vivo.
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