Verlag des Forschungszentrums Jülich
JUEL-3543
Neveling, Ute
Struktur- und Funktionsanalyse des Pyruvatdehydrogenase Multienzymkomplexes aus Zymomonas mobilis und Charakterisierung der komplexkodierenden Gene
118 S., 1998
The pryuvate dehydrogenase complex (PDHC) of the gram-negative bacterium Zymomonas
mobilis was purified to homogeneity. From 250 g cells 1 mg PDHC was isolated with
a specific activity of 12. 6 U/mg protein. Analysis of subunit composition revealed
a pyruvate dehydrogenase (E1) consisting of the two subunits E1 [alpha] (38 kD) and E1 [beta] (56 kD), a dihydrolipoamide acetyltransferase (E2) of 48 kD and a lipoamide
dehydrogenase (E3) of 50 kD. The E2 core of the complex is arranged to form a
pentagonal dodecahedron, as shown by electron microscopic images, resembling the
quartenary structures of PDHCs from gram-positive bacteria and eukaryotes. The PDH
complex encoding genes were identified by hybridization experiments and sequence
analysis in two separate gene regions in the genome of Z. mobilis. The genes pdhA
[alpha] (1065bp) and pdhA[beta] (1389bp) encoding the E1[alpha] and E1[beta] subunits of the E1 component
were located downstream of the gene encoding enolase. The pdhB (1323 bp) and lpd
(1401 bp) genes, encoding for the E2 and E3 components were identified in an
unrelated gene region together with an 450 bp ORF of unknown function in the order
pdhB-ORF2-lpd. Highest similarities of the gene products of the pdhA[alpha], pdhA[beta] and
pdhB genes were found with the corresponding enzymes of Saccharomyces cerevisiae
and other eukaryotes. The product of the pdhB gene contains a single lipoyl domain
as is the case with the dihydrolipoamide acetyltransferase of S. cerevisiae and
numerous other organisms. The E1[beta] subunit of pyruvate dehydrogenase was found to
contain an amino terminal lipoyl domain, a property which is unique among pyruvate
dehydrogenases.
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