Alanine aminotransferase: properties and distribution in the desert locust, Schistocerca gregaria

Silencing of a putative alanine aminotransferase (ALT) gene influences free amino acid composition in hemolymph and fecundity of the predatory bug, Cyrtorhinus lividipennis Reuter

In Asian rice systems, Cyrtorhinus lividipennis Reuter is an important predator that preys on rice planthopper eggs and young nymphs, as a primary food source. Alanine aminotransferase (ALT) acts in many physiological and biochemical processes in insects. We cloned the full-length complementary DNA of C. lividipennis ClALT. Expression analysis showed higher expression in the fat body and midgut compared to other tissues. It is expressed in all C. lividipennis developmental stages and at least four organs. Silencing of ClALT by RNA interference significantly decreased the ClALT enzyme activity and ClALT expression compared to dsGFP-treated controls at 2 days after emergence (DAE). Silencing of ClALT influenced free hemolymph amino acid compositions, resulting in a reduction of Aspartic acid (Asp) and Alanine (Ala) proportions, and increased Cysteine (Cys) and Valine (Val) proportions in females at 2 DAE. dsClALT treatments led to decreased soluble total protein concentrations in ovary and fat body, and to lower reduced vitellogenin (Vg) expression, body weight, and the numbers of laid eggs. The double-stranded RNA viruse treatments also led to prolonged preoviposition periods and hindered ovarian development. Western blot analysis indicated that silencing ClALT also led to reduced fat body Vg protein abundance at 2 DAE. These data support our hypothesis that ClALT influences amino acid metabolism and fecundity in C. lividipennis.

Effect of antimicrobial Peptide, nisin, on the reproductive functions of rats

Our previous studies have demonstrated that naturally occurring peptide, Nisin possess antibacterial activity and did not interfere with rabbit vaginal mucosa. In this study, the reproductive toxicity of the Nisin in male rats was evaluated. Rats were fed orally with Nisin (10, 25, and 50 mg/kg/day) for 13 weeks. No treatment related mortality was observed. The body weight gain, food consumption and serum biochemical parameters were at par with the control group. Histomorphology of the selected reproductive (testis, epididymis, ventral prostate, and seminal vesicle) and nonreproductive (liver and kidney) tissues was observed to be normal. There was no treatment-related increase or decrease in the expression of testis-specific genes (c-Kit, GATA-1, and HILS-1) and the activity levels of epididymal α-glucosidase, ventral prostate alkaline phosphatase (AlP), liver alanine aminotransferase (AlAT) and aspartate aminotransferase (AAT). Fructose and lactic acid levels in the seminal vesicles also remained unchanged. These studies suggest that Nisin did not affect the normal physiology of these organs. In addition, no adverse effects were observed on the reproductive performance of Nisin-treated male rats and their offspring. In conclusion, the current studies support our earlier studies, which demonstrated suitability of Nisin as a safe and effective microbicide.

Studies on alanine aminotransferase in nematodes

L-alanine aminotransferase was demonstrated in a range of gastrointestinal, free-living and entomophagous nematodes. As in mammals, nematode L-alanine aminotransferase was found to exist in the form of mitochondrial and cytosolic isoenzymes. Whilst the majority of nematode enzymes exhibited a greater overall capacity for L-alanine synthesis than for L-alanine catabolism in vitro, the opposite was true for rat liver L-alanine aminotransferase. In contrast with rat liver, certain gastrointestinal nematodes were apparently able to transaminate D-alanine at low rates. H. contortus cytosolic L-alanine aminotransferase differed significantly from the mammalian enzyme with respect to both thermal stability and response to potential protective reagents.