C. Bruntner et C. Bormann, THE STREPTOMYCES-TENDAE TU901 L-LYSINE 2-AMINOTRANSFERASE CATALYZES THE INITIAL REACTION IN NIKKOMYCIN-D BIOSYNTHESIS, European journal of biochemistry, 254(2), 1998, pp. 347-355
Protein P8 was previously identified as a putative nikkomycin biosynth
esis protein. The gene (nikC) encoding protein P8 was cloned from the
Streptomyces tendae Tii901 nikkomycin gene cluster and sequenced. The
nikC gene was inactivated by inserting a kanamycin resistance cassette
; the mutant did not produce the biologically active nikkomycins I, J,
X, and Z, but accumulated the nucleoside moieties nikkomycins C-X and
C-Z. The mutant was complemented to nikkomycin production (I, J, X, Z
) by nikC expressed from the mel promoter of the vector pIJ702. Furthe
rmore, the nikkomycin-negative phenotype was reversed by the addition
of picolinic acid, a precursor of the peptidyl moiety of nikkomycins (
nikkomycin D), into the culture medium. The nikC gene was expressed in
Escherichia coil and identified and characterized at the enzyme level
. NikC encodes an L-lysine 2-aminotransferase, and the activity was ex
clusively detected in nikkomycin producers and its presence correlated
to nikkomycin production. The nikC-inactivated mutant grew with L-lys
ine as sole source of nitrogen and carbon, indicating that L-lysine 2-
aminotransferase is not required for lysine catabolism. Our results id
entified the nikC-encoded L-lysine 2-aminotransferase as the nikkomyci
n biosynthetic enzyme that catalyzes the initial reaction in nikkomyci
n D biosynthesis. The NikC protein belongs to a novel family of pyrido
xamine or pyridoxal-phosphate-dependent dehydrases and aminotransferas
es, some of which are involved in dideoxy- and deoxy-aminosugar biosyn
thesis.