NAD-preferring malic enzyme: localization, regulation and its potential role in herring (Clupea harengus) sperm cells.

Herring spermatozoa exhibit a high activity of NAD-preferring malic enzyme (NAD-ME). This enzyme is involved in the generation of NADH or NADPH in the decarboxylation of malate to form pyruvate and requires some divalent cations to express its activity. In order to confirm that NAD-ME isolated from herring sperm cells is localized in mitochondria, we performed immunofluorescent analysis and assayed spectrophotometrically the malic enzyme reaction.

Purification and stability of octameric mitochondrial creatine kinase isoform from herring (Clupea harengus) organ of vision.

Creatine kinases (CKs) constitute a large family of isoenzymes that are involved in intracellular energy homeostasis. In cells with high and fluctuating energy requirements ATP level is maintained via phosphocreatine hydrolysis catalyzed by creatine kinase. In contrast to invertebrates and higher vertebrates, in poikilothermic vertebrates the adaptations for the regulation of energy metabolism by changes in the oligomeric state of CK isoforms are not well known.

Purification and properties of malic enzyme from herring Clupea harengus spermatozoa.

Herring spermatozoa exhibit higher activity of malic enzyme (ME) than Atlantic salmon (Salmo salar), brown trout (Salmo trutta), carp (Cyprinus carpio) and African catfish (Clarias gariepinus) spermatozoa. Two molecular forms of ME are present in herring spermatozoa: an NAD-preferring malic enzyme with very high activity and an NADP-specific malic enzyme with much lower activity (ratio about 33:1). NAD-preferring ME was purified by chromatography on DEAE-Sepharose, Red Agarose and Sephadex G-200 to a specific activity of 36 μmol/min/mg protein and NADP-specific ME on DEAE-Sepharose and 2'5'-ADP Sepharose.

[Creatine kinase isoenzymes--characterization and functions in cell].

Creatine kinase (CK, EC 2.7.3.

Purification and some properties of two creatine kinase isoforms from herring (Clupea harengus) spermatozoa.

Creatine kinase (CK, EC 2.7.3.

Characterization of creatine kinase isoforms in herring (Clupea harengus) skeletal muscle.

It is known that mitochondrial creatine kinase (MtCK) in mammals is always expressed in conjunction with one of the cytosolic forms of creatine kinase (CK), either muscle-type (MM-CK) or brain-type (BB-CK) in tissues of high, sudden energy demand. The two creatine kinase (CK) isoforms were detected in herring (Clupea harengus) skeletal muscle: cytosolic CK and mitochondrial CK (MtCK) that displayed the different electrophoretic mobility. These isoforms differ in molecular weight and some biochemical properties.

In vitro adenine nucleotide catabolism in African catfish spermatozoa.

It has been shown recently that African catfish (Clarias gariepinus) spermatozoa possess relatively low ATP content and low adenylate energy charge (AEC). One of the possible explanations for this phenomenon is that the spermatozoa actively catabolize adenine nucleotides. A relatively high rate of such catabolism could then contribute to the low ATP concentration and low adenylate energy charge observed in the spermatozoa in vitro.

Inhibition by tributyltin of herring skeletal muscle lactate dehydrogenase activity.

The activity of herring (Clupea harengus) skeletal muscle lactate dehydrogenase (EC 1.1.1.

Enzyme activities in fish spermatozoa with focus on lactate dehydrogenase isoenzymes from herring Clupea harengus.

The activities of NAD- and NADP-dependent dehydrogenases and creatine kinase were compared in extracts of spermatozoa from herring (Clupea harengus), carp (Cyprinus carpio) and catfish (Clarias gariepinus). The activity of malic enzyme in herring spermatozoa was approximately 5 and 36 times higher than in carp and catfish spermatozoa. In contrast, lactate dehydrogenase activity in herring spermatozoa was very low.

Quantitative determination of creatine kinase release from herring (Clupea harengus) spermatozoa induced by tributyltin.

Creatine kinase (CK, ATP creatine phosphotransferase, EC 2.7.3.