Effects of niacin deficiency on the levels of soluble proteins and enzyme activities in various tissues of Japanese quail

Mitochondrial function and toxicity: role of the B vitamin family on mitochondrial energy metabolism

The B vitamins are water-soluble vitamins required as coenzymes for enzymes essential for cell function. This review focuses on their essential role in maintaining mitochondrial function and on how mitochondria are compromised by a deficiency of any B vitamin. Thiamin (B1) is essential for the oxidative decarboxylation of the multienzyme branched-chain ketoacid dehydrogenase complexes of the citric acid cycle. Riboflavin (B2) is required for the flavoenzymes of the respiratory chain, while NADH is synthesized from niacin (B3) and is required to supply protons for oxidative phosphorylation. Pantothenic acid (B5) is required for coenzyme A formation and is also essential for alpha-ketoglutarate and pyruvate dehydrogenase complexes as well as fatty acid oxidation. Biotin (B7) is the coenzyme of decarboxylases required for gluconeogenesis and fatty acid oxidation. Pyridoxal (B6), folate and cobalamin (B12) properties are reviewed elsewhere in this issue. The experimental animal and clinical evidence that vitamin B therapy alleviates B deficiency symptoms and prevents mitochondrial toxicity is also reviewed. The effectiveness of B vitamins as antioxidants preventing oxidative stress toxicity is also reviewed.

Purification of soluble acetylcholinesterase from Japanese quail brain by affinity chromatography

The purification of a soluble acetylcholinesterase from Japanese quail brain using affinity chromatography on concanavalin A-Sepharose and edrophonium-Sepharose is described. The affinity matrix was synthesized by coupling an inhibitor edrophonium to epoxy-activated Sepharose. Acetylcholinesterase was purified 10,416-fold with a specific activity of 2500 U/mg protein. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and mercaptoethanol gave only one band with a molecular weight of 62.5 kDa. The molecular weight of the purified acetylcholinesterase was estimated to be 245.5 kDa by gel chromatography on Sephacryl S-200 under nondenaturing conditions. Based on the molecular weight obtained by both SDS-PAGE and gel filtration the purified acetylcholinesterase was assumed to be a tetrameric form.

Effects of nicotinamide coenzymes on the stability of enzyme activities and proteins in niacin-deficient quail tissues against trypsin treatment

The stability of liver and muscle enzymes and proteins in niacin-deficient quail towards trypsin treatment in the presence and absence of coenzymes, NAD or NADP, was characterized. The protection of liver dehydrogenases by coenzymes was low when they are subjected to trypsin digestion for 60 min. In contrast, in the muscle there was substantial protection against trypsin inactivation of glyceraldehyde-3-phosphate dehydrogenase by NAD and of 6-phosphogluconate dehydrogenase by NADP. Among all enzymes tested, glyceraldehyde-3-phosphate dehydrogenase showed the greatest protection against trypsin inactivation by NAD. SDS-polyacrylamide gel electrophoresis demonstrated that muscle proteins from the niacin-deficient group were more substantially protected compared to control and pair-fed groups when liver and muscle extracts were spiked with NAD and subjected to trypsin digestion. Overall results suggest that niacin deficiency exerted specific destabilizing effects on the stability of enzymes and proteins in muscle.

Effects of 6-aminonicotinamide on levels of soluble proteins and enzyme activities in various tissues of Japanese quail

The effects of 6-aminonicotinamide (6-AN) on the levels of soluble proteins and enzyme activities in various tissues of Japanese quail were investigated. SDS-polyacrylamide gel electrophoresis showed that the soluble proteins with molecular masses corresponding to 160.4 and 52.5 kDa were either missing or present at lower concentrations in the brain of the 6-AN treated group compared to those in the control group. The soluble liver proteins with molecular masses 200, 120 and 70.5 kDa were missing in the treated group compared to those in the control while those of a molecular mass 15.1 kDa were found to be present at higher concentrations. Similarly, treatment with 6-AN decreased the concentration of soluble proteins in pectoral muscle with molecular masses 92.3, 54.5, 43.5, 41.2, 34.5, 27.5, 20.1 and 17.5 kDa and increased those with molecular masses 96.5, 37.7, 25.0, 19.3, 16.6, 13.8 and 10.8 kDa. In the heart, soluble proteins with molecular mass 84.6 kDa were increased. There was a marked reduction in the treatment group in the concentration of NAD in pectoral muscle but not in other tissues. A similar observation was also made with total RNA levels. The specific activity of malic enzyme was markedly increased by 6-AN treatment in the kidney and pectoral muscle but reduced in the liver. 6-Phosphogluconate dehydrogenase and lactate dehydrogenase activities were markedly reduced in the liver. Glyceraldehyde-3-phosphate dehydrogenase activity was significantly decreased in liver and pectoral muscle. NAD glycohydrolase activity was markedly decrease in pectoral muscle. Acetylcholinesterase activity was markedly reduced in liver but was enhanced in pectoral muscle. The results suggest that the metabolic actions of 6-AN are specific for certain proteins in the liver and muscle with the effect being most pronounced in muscle. The effects are also quite distinct from those by its analogue 3-acetylpyridine.

Effects of NAD or NADP on the stability of liver and pectoral muscle enzymes in 3-acetylpyridine treated quail by heat and trypsin

(1) The effects of long term treatment with 3-acetylpyridine on the stability of enzymes towards heat and trypsin treatment were studied. (2) In the liver NAD or NADP provided a similar degree of protection against heat inactivation at 55 degrees C for 6-phosphogluconate dehydrogenase (24%), glyceraldehyde-3-phosphate dehydrogenase (24%) and malic enzyme (20%), low level of protection of lactate dehydrogenase (13%) but didn't affect acetylcholinesterase at all. In the muscle, however, there was substantial protection against heat inactivation by coenzyme of glyceraldehyde-3-phosphate dehydrogenase (52%), an intermediate level of protection of lactate dehydrogenase (25%), low level of protection of 6-phosphogluconate dehydrogenase (17%) and malic enzyme (17%) and almost no protection of acetylcholinesterase. (3) In the susceptibility towards trypsin a low but similar degree of protection for dehydrogenases by coenzymes was observed in the liver whereas in the muscle there was substantial protection against trypsin inactivation by NAD of glyceraldehyde-3-phosphate dehydrogenase, an intermediate level of protection of 6-phosphogluconate dehydrogenase and malic enzyme and very little protection of lactate dehydrogenase but no protection of acetylcholinesterase. Among enzymes tested, glyceraldehyde-3-phosphate dehydrogenase showed the greatest protection against heat and trypsin inactivation by NAD. (4) The results suggest that the effect of 3-acetylpyridine treatment on the stability of muscle glyceraldehyde-3-phosphate dehydrogenase appears to be quite specific and selective.