FEMS MicrobiologyLetters 82 (1991) 209-214 ,~3 1991 Federation of European Microbiological Societies 0378-1097/91/$03.50 Published by Elsevier ADONIS 037810979100375F 209 FEMSLE 04570 The route of lysine breakdown in Candida tropicalis Peter J. Large and Anne Robertson Department of Applied Biology, Unit,ersityof Hull, Hull, U.K. Received and accepted 21 May 1991 Key words: N6-Acetyllysine; 5-Acetamidovalerate; 5-Aminovalerate; Lysine N6-acetyltransferase; N6-Acetyllysine aminotransferase; 5-Aminovalerate aminotransferase; Candida tropicalis 1. SUMMARY Candida tropicalis was found to contain high levels of the following enzymes after growth in defined medium on L-lysine as sole nitrogen source: L-lysine N6-acetyltransferase, N6-acetyl - lysine aminotransferase, and aminotransferase activity for 5-aminovalerate and 4-aminobutyrate. Extracts were also capable of converting 5- acetamidovalerate (and 4-acetamidobutyrate) to acetate. N6-Acetyllysine however, only gave rise to acetate in the presence of 2-oxoglutarate, NAD + and thiamine pyrophosphate. These activ- ities were undetectable or present in much lower concentrations in cells that had been grown on ammonium sulphate as sole nitrogen source. It is concluded that L-lysine is degraded in this organ- ism via N6-acetyllysine, 5-acetamidovalerate and 5-aminovalerate, both nitrogen atoms being re- moved by transamination. Correspondence to: P.J. Large, Department of Applied Biol- ogy, The University, Hull HU6 7RX, U.K. 2. INTRODUCTION Most yeasts (with the notable exception of Saccharomyces cerevisiae) are able to use lysine as sole nitrogen source for growth [1]. Three reac- tions for the initiation of lysine breakdown have been described in yeasts [2], one involving transarnination of lysine at the 6-amino group with either 2-oxoglutarate [3] or pyruvate [4] as amino acceptor; one involving lysine 6-dehydro- genase [2]; and a route (Fig. 1) involving the acetylation of lysine at the 6-amino group fol- lowed by transamination of the N6-acetyllysine [5]. The next stages are oxidative decarboxylation of 2-oxo-6-acetamidohexanoate to 5-acetamido- valerate, deacetylation of the latter to 5-amino- valerate and transamination of this to glutarate semialdehyde, thereby removing the second amino group. Evidence for the occurrence of one or more of the enzymes of this route has been obtained in Williopsis (Hansenula) saturnus [6], Yarrowia lipolytica [7] and Candida maltosa [8], as well as in the filamentous fungus Rhizoctonia leguminicola [9]. In this paper we have screened various yeast Downloaded from https://academic.oup.com/femsle/article-abstract/82/2/209/637740 by guest on 11 June 2020