Molecular cloning of chicken hepatic histidase and protein regulation of the mRNA expression of chicken hepatic histidase and malic enzyme
Chendrimada, Thimmaiah Ponnappa
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After obtaining a cDNA clone for chicken hepatic histidase, experiments were conducted to study the regulation of histidase mRNA expression by dietary protein concentrations. Histidase mRNA expression was increased within 3 h when chicks consumed higher levels of dietary protein. Increasing the dietary concentration of histidine did not alter hepatic histidase mRNA expression. The rapid increase in histidase mRNA levels in response to dietary protein intake is similar to the rapid decrease seen in malic enzyme mRNA levels in chicks fed the high protein diets. Glucagon was shown to regulate the mRNA expression of both the enzymes, and could act as a mediator for the effect of dietary protein on histidase and malic enzyme mRNA expression since an increase in dietary protein intake elevated plasma glucagon concentration within 1 h. While histidase mRNA expression seems to be regulated by concentrations of specific amino acids in the diet, malic enzyme mRNA expression seems to be regulated by the total protein or nitrogen level of the diet. Finally, addition of synthetic glutamic acid to a practical corn-soy poultry diet reduced the amount of abdominal fat present in broiler chicks at slaughter.