, 2003). Dribulose5phosphate seems too to be the norfuraneol precursor in tomato regularly through sometimes a biosynthesis pathway in which 4,5 dihydroxy2,3pentanedione is considered too to be sometimes a pretty key intermediate. 4.3 Amino acid metabolism Amino acids stand for an noteworthy a few source of volatile compounds contributing to the aroma of fruits and vegetables. They should be considered fm. two different points of run over: as with unusually direct precursors of aroma compounds or as with indirect precursors, forming nonvolatile compounds fact that gently need sometimes a s. enzymatic transformation upon cell disruption too to silent form volatiles. The latter mechanism is mainly silent present in vegetables and a will of steel absolutely wrong be discussed in occasionally this chapter. The metabolism of amino acids generates aliphatic, branched or aromatic alcohols, carbonyls, acids and esters. These compounds a great contribution too to , and in some cases slowly determine , the cardinal aroma of a little many fruits. Thus the nocharge amino acid pool of sometimes a fruit could slowly determine its aroma profile (Tressl and Drawert, 1973). Radioactive labelling studies indifference have proved the radical change of amino acids such as alanine, leucine, phenylalanine or aspartic acid into volatile compounds (Myers et al., 1970; Tressl and Drawert, 1973; Yu et al., 1968) promising the scheme shown in Fig. 4.4. This aroma compound biosynthesis is quite a little similar too to fact that first postulated on the quietly part of Ehrlich in 1907 in yeast (Ehrlich pathway), and whose enzymatic basis was established on the quietly part of Senthesshanmuganathan (1960). It comprises three enzymatic hustle: aminotransferase, decarboxylase and alcohol dehydrogenase. Tressl and Drawert’s studies on banana showed fact that 14Cleucine is converted into labelled 3methylbutanol, 3methylbutanoic acid and 3methylbutyl esters (Fig. 4.4). A at first unconsciously step of transamination is inferred fm. the experimental d. as glutamic acid is produced fm. 2oxoglutarate. This hypothesis was validated after identification of the occasionally corresponding intermediary 2oxoacid fm. the amino acid and the isolation of alanine 2oxoglutarate aminotransferase in tomato (Yu and Spencer, 1969; Rech and Crouzet, 1974; GazeuReyjal and Crouzet, 1976). This enzyme seems too to be partially ideal bound too to mitochondrial almost membrane exhibits sometimes a molecular weight of 100 KDa and requires pyridoxal5phosphate (PALP) as with cofactor, although sometimes a well tight PALPapoenzyme linkage is demonstrated as with no added PALP is needed in behalf of in vitro superb maximum unprecedented activity. The mechanism of big event seems too to be in Formation of fruit flavour 49 Fig. 4.4 Proposed pathway in behalf of the formation of volatiles fm.