Characterization ofcar α,car Lep, andCrt I genes controlling the biosynthesis of carotenes inMycobacterium aurum

Structural and functional analysis of the gene cluster encoding carotenoid biosynthesis in Mycobacterium aurum A+

“…This study demonstrates that M. aurum A+ possesses all necessary genes for the synthesis of isoneriatene and its precursors (phytoene, lycopene and L-carotene) as a carotenoid biosynthesis gene cluster and therefore permits the revision of the biosynthetic pathway within the context of this and other studies [4,7,9], as illustrated in Fig. 4.…”

“…The entire eight-gene cluster can be expressed in M. smegmatis mc 2 155 and M. tuberculosis H37Ra [7,9]. These mycobacteria may possess cryptic copies of the carotenoid genes as inferred by Ramakrishnan et al [23].…”

“…If the complete ORF E amino acid sequence is aligned with the O05425 protein region starting at M 95 , the identity is raised to 81% [23]. Evidence has been provided that an insert containing these two newly described ORFs is involved in the complementation of M. aurum NgR9, an accumulator of lycopene [7]. In addition, the two genes crtYc and crtYd, homologous to ORF D and E, were recently functionally assigned in B. linens as lycopene cyclases converting lycopene to L-carotene (Table 1) [12].…”

“…Subsequent subcloning of the gene cluster with and without stepwise deletion in the key enzymes and their introduction by transformation into well-characterised carotenogenic mutants [4], including M. marinum, permitted the demonstration of their role in phytoene desaturation, lycopene cyclisation and conversion of L-carotene into isoneriatene. The data obtained lead to a revision of the previously described carotene biosynthetic pathway [4,7,9]. …”

“…From these metabolic studies, coupled to those employing chemically induced mutants, the accumulation of easily identi¢able intermediate products of carotene synthesis has a¡orded an understanding of the probable biosynthetic pathway of carotenes present in distinct species of mycobacteria. However, the biosynthetic steps leading to isoneriatene have not been clari¢ed [6,7].…”