AROMATIC AND BRANCHED-CHAIN AMINO-ACIDS C ATABOLISM IN LACTOCOCCUS-LACTIS

The enzymatic degradation of amino acids in cheeses is believed to gen erate aroma compounds. In lactococci, transamination is the first step in the degradation of aromatic and branched-chain amino acids. Severa l aminotransferase activities have been detected and, an aromatic-amin otranferase has been purified and characterised. Ketoacids resulting f rom transamination are mainly degraded to carboxylic acids or to hydro xyacids, depending on the reaction conditions. These degradations coul d be catalysed by lactate dehydrogenase and pyruvate dehydrogenase whi ch are involved in pyruvate catabolism. However, we also suggest the e xistence of other dehydrogenase, more specific for ketoacids from amin o acids. Whereas amino acids catabolism need to be clarified, we can s tate that lactococci have the enzymatic equipment required for the tra nsformation of aromatic and branched chain amino acids to volatile aro ma compounds. (C) Inra/Elsevier, Paris.