BUTYRATE:ACETOACETYL-CoA TRANSFERASE ACTIVITY IN BOVINE RUMEN EPITHELIUM

Enzymatic activity catalyzing transacylation between butyrate and acetoacetyl-CoA was detected in homogenate and cell-free extracts of bovine rumen epithelium which was obtained fresh from the slaughter house. The enzyme is active over a wide pH range with the maximum between 6.5 and 8.0. The rate of disappearance of acetoacetyl-CoA at 310 nm in the presence of butyrate was 19 μmol/h per gram wet weight tissue at 22 °C. When acetate and propionate were used as substrates, acetoacetyl-CoA removal rates were 8.7 and 14.5 μmol/h per gram wet weight, respectively. Acetoacetate, the product of the transferase reaction was measured enzymatically. Other products formed including acetyl-CoA, propionyl-CoA and butyryl-CoA were identified chromatographically. This transacylation reaction has an impact on energy conservation in the rumen epithelium. Activities of 3-oxo acid CoA transferase (EC 2.8.3.5) and D(–)-3-hydroxybutyrate dehydrogenase (EC 1.1.1.30), key enzymes in rumen epithelial ketogenesis, were 26 and 16 μmol/h per gram wet weight tissue. Key words: Butyrate:acetoacetyl-CoA transferase, bovine, rumen, epithelium