In:
Applied and Environmental Microbiology, American Society for Microbiology, Vol. 65, No. 5 ( 1999-05), p. 1973-1979
Abstract:
d -Pantothenate is synthesized via four enzymes from ketoisovalerate, which is an intermediate of branched-chain amino acid synthesis. We quantified three of these enzyme activities in Corynebacterium glutamicum and determined specific activities ranging from 0.00014 to 0.001 μmol/min mg (protein) −1 . The genes encoding the ketopantoatehydroxymethyl transferase and the pantothenate synthetase were cloned, sequenced, and functionally characterized. These studies suggest that panBC constitutes an operon. By using panC , an assay system was developed to quantify d -pantothenate. The wild type of C. glutamicum was found to accumulate 9 μg of this vitamin per liter. A strain was constructed (i) to abolish l -isoleucine synthesis, (ii) to result in increased ketoisovalerate formation, and (iii) to enable its further conversion to d -pantothenate. The best resulting strain has ilvA deleted from its chromosome and has two plasmids to overexpress genes of ketoisovalerate ( ilvBNCD ) and d -pantothenate ( panBC ) synthesis. With this strain a d -pantothenate accumulation of up to 1 g/liter is achieved, which is a 10 5 -fold increase in concentration compared to that of the original wild-type strain. From the series of strains analyzed it follows that an increased ketoisovalerate availability is mandatory to direct the metabolite flux into the d -pantothenate-specific part of the pathway and that the availability of β-alanine is essential for d -pantothenate formation.
Type of Medium:
Online Resource
ISSN:
0099-2240
,
1098-5336
DOI:
10.1128/AEM.65.5.1973-1979.1999
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
1999
detail.hit.zdb_id:
223011-2
detail.hit.zdb_id:
1478346-0
SSG:
12
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