Le catabolisme des acides aminés aromatiques et des acides aminés à chaîne ramifiée chez Lactococcus lactis

Abstract

Aromatic and branched chain amino acids cataboIism in Lactococcus lactis. The enzymatic degradation of amino acids in cheeses is believed to generate aroma compounds. In lac- tococci, transamination is the first step in the degradation of aromatic and branched-chain amino acids. Several aminotransferase activities have been detected and, an aromatic-aminotranferase has been purified and characterised. Ketoacids resulting from transamination are mainly degra- ded to carboxylic acids or to hydroxyacids, depending on the reaction conditions. These degra- dations could be catalysed by lactate dehydrogenase and pyruvate dehydrogenase which are involved in pyruvate catabolism. However, we also suggest the existence of other dehydrogenases, more specifie for ketoacids from amino acids. Whereas amino acids catabolism need to be ela- rified, we can state that lactococci have the enzymatic equipment required for the transformation of aromatic and branched chain ami no acids to volatile aroma compounds. © Inra/Elsevier,