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.