The genes lmbB1 and lmbB2 of Streptomyces lincolnensis encode enzymes involved in the conversion of l -tyrosine to propylproline during the biosynthesis of the antibiotic lincomycin A

Abstract

The genes lmbA,B1,B2 in the lincomycin A production gene cluster of Streptomyces lincolnensis were shown to form a common transcription unit with the promoter located directly upstream of lmbA. The proteins LmbB1 (mol. mass, 18 kDa) and LmbB2 (mol. mass 34 kDa), when over-produced together in Escherichia coli, brought about enzyme activities for the specific conversion of both L-tyrosine and L-3,4-dihydroxyphenylalanine (L-DOPA) to a yellow-colored product. The LmbB1 protein alone catalyzed the conversion of L-DOPA, but not of L-tyrosine. The purified LmbB1 protein showed a Km for L-DOPA of 258.3 microM. The L-tyrosine converting activity could not been demonstrated in vitro. The preliminary interpretation of these data suggests that the protein LmbB1 is an L-DOPA extradiol-cleaving 2,3-dioxygenase and that the protein LmbB2, either alone or in accord with LmbB1, represents an L-tyrosine 3-hydroxylase. This sequence of putative oxidation reactions on L-tyrosine seems to represent a new pathway different from the ones catalyzed by mammalian L-tyrosine hydroxylases or the wide-spread tyrosinases. The protein LmbA seemed not to be involved in this process. The labile, yellow-colored product from L-DOPA could not be converted to a picolinic acid derivative [3-(2-carboxy-5-pyridyl)alanine] in the presence of ammonia. Therefore, it probably is not a derivative of a cis, cis-3-hydroxymuconic acid semialdehyde; instead, its speculative structure represents a heterocyclic precursor of the propylhygric acid moiety of lincomycin A.

The Novel Transcriptional Regulator LmbU Promotes Lincomycin Biosynthesis through Regulating Expression of Its Target Genes in Streptomyces lincolnensis

“…L-Tyrosine was identified as a precursor of PPL through stable-isotope labeling (10), and it is converted into L-3,4-dihydroxyphenylalanine (L-DOPA) and then into 4-(3-carboxy-3-oxo-propenyl)-2,3-dihydro-1H-pyrrole-2-carboxylic acid (product 1) by the L-tyrosine hydroxylase LmbB2 and the L-DOPA-2,3-dioxygenase LmbB1 (11,12). In the recent report, it was proposed that product 1 undergoes methylation by LmbW to generate product 2 (13,14).…”

Biosynthesis of Sibiromycin, a Potent Antitumor Antibiotic

“…Labeling experiments have identified L-tyrosine as the biosynthetic precursor for the hydropyrrole moieties of PBDs, as well as of lincomycin A (2, 11). The functional assignment of the biosynthetic enzymes involved in this transformation with the exception of the first two steps catalyzed by a tyrosine hydroxylase and an L-DOPA 2,3-dioxygenase (31,33) remains undetermined in the PBDs and lincomycin A biosyntheses (10,37). We propose a common biosynthetic route for the formation of 4-propylidene-tetrahydropyrrole-2-carboxylic acid in the PBDs and lincomycin biosyntheses, the last intermediate in common in the anthramycin, sibiromycin, and lincomycin A biosyntheses (Fig.…”

Biosynthetic Pathway for Mannopeptimycins, Lipoglycopeptide Antibiotics Active against Drug-Resistant Gram-Positive Pathogens

“…The mannopeptimycin gene cluster contains a single methyltransferase gene, mppJ, and its protein product (MppJ) contains motifs involved in binding the methyl-donating cofactor S-adenosyl methionine (SAM). The closest homology match to MppJ is LmbW (27% identical and 43% similar), a protein of unassigned function encoded within the lincomycin gene cluster in Streptomyces lincolnensis (30). Lincomycin, an alkaloid antibiotic, contains the modified amino acid propyl-L-proline.…”