|
type |
Journal Article |
authors |
Ferreira, G. C.; Dailey, H. A. |
title |
Expression of mammalian 5-aminolevulinate synthase in Escherichia coli. Overproduction, purification, and characterization |
journal |
J Biol Chem |
Activity |
2.3.1.37 |
Family |
2.3.1.37 |
sel |
selected |
ui |
8416963 |
year |
(1993) |
volume |
268 |
number |
1 |
pages |
584-90 |
| |
keywords |
5-Aminolevulinate Synthetase/genetics/isolation & purification/*metabolism |
abstract |
5-Aminolevulinate synthase catalyzes the first step of the heme biosynthetic pathway in nonplant higher eukaryotes. A cDNA encoding for the mouse erythroid 5-aminolevulinate synthase (Schoenhaut, D. S., and Curtis, P.J. (1986) Gene (Amst.) 48, 55-63) has been expressed in Escherichia coli, using the alkaline phosphatase promoter, to a level of 50-60% of the total bacterial protein. Aminolevulinate synthase was overexpressed in an active form and, therefore, was able to rescue hemA mutants, which are unable to grow in the absence of 5-aminolevulinate. A simple purification from the aminolevulinate synthase-overproducing bacterial strain yielded approximately 50 mg of protein, in a high state of purity, per liter of bacterial culture. Moreover, the expressed aminolevulinate synthase could be easily concentrated up to 6- 8 mg/ml. Significantly, recombinant aminolevulinate synthase retained physical and catalytic properties identical to those of natural sources. These include the dimeric structure, subunit molecular mass, and pyridoxal 5'-phosphate as an essential cofactor. Removal of the pyridoxal 5'-phosphate led to complete loss of activity. However, the apoenzyme could be readily reconstituted by incubation with 20 microM 5'-pyridoxal phosphate. The Km values are 51 mM for glycine and 55 microM for succinyl-CoA, in the same range of the Km values determined for the nonrecombinant enzyme. This report describes the overexpression of a mammalian 5-aminolevulinate synthase in E. coli and its purification from an overproducing strain. The ready availability of the pure, cloned, sequenced erythroid 5-aminolevulinate synthase makes it possible now for questions pertinent to the enzyme's structure, mechanism, and regulation to be addressed. |
last changed |
2009/01/12 14:29 |
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