Functional analysis of the methylmalonyl‐CoA epimerase from Caenorhabditis elegans

Abstract

Methylmalonyl‐CoA epimerase (MCE) is an enzyme involved in the propionyl‐CoA metabolism that is responsible for the degradation of branched amino acids and odd‐chain fatty acids. This pathway typically functions in the reversible conversion of propionyl‐CoA to succinyl‐CoA. The Caenorhabditis elegans genome contains a single gene encoding MCE (mce‐1) corresponding to a 15 kDa protein. This was expressed in Escherichia coli and the enzymatic activity was determined. Analysis of the protein expression pattern at both the tissue and subcellular level by microinjection of green fluorescent protein constructs revealed expression in the pharynx, hypodermis and, most prominently in body wall muscles. The subcellular pattern agrees with predictions of mitochondrial localization. The sequence similarity to an MCE of known structure was high enough to permit a three‐dimensional model to be built, suggesting conservation of ligand and metal binding sites. Comparison with corresponding sequences from a variety of organisms shows more than 1/6 of the sequence is completely conserved. Mutants allelic to mce‐1 showed no obvious phenotypic alterations, demonstrating that the enzyme is not essential for normal worm development under laboratory conditions. However, survival of the knockout mutants was altered when exposed to stress conditions, with mutants surprisingly showing an increased resistance to oxidative stress.

Propionyl-CoA and adenosylcobalamin metabolism in Caenorhabditis elegans: Evidence for a role of methylmalonyl-CoA epimerase in intermediary metabolism

“…The deletion of mmab-1 harbored in strain VC974 has been described by the generating laboratory and appears to remove the C-terminal exon that has high homology with the adenosyltransferase domain. Strain RB512 has previously been shown to harbor a deletion of the mce-1 gene [15]. Propionate incorporation and metabolic analysis of the mce-1 mutant have not been previously described.…”

“…The methylmalonyl-CoA epimerase (mce-1) of C. elegans has been studied [15]. A deletion mutant has no phenotype and exhibits relative resistance to oxidative stress.…”

Genetic and genomic systems to study methylmalonic acidemia

“…The existence of such highly conserved homologues in C. elegans is strong evidence that this primitive animal possesses the same pathway for the conversion of propionate to succinate as is found in humans. Furthermore, the existence and functional demonstration of MCR enzymatic activity in C. elegans supports this hypothesis [18].…”

“…The gene has been identified in C. elegans and studied in a deletion mutant, which is viable and relatively resistant to oxidative stress [18]. A murine homologue is predicted to exist and construction of a mouse model may also be useful.…”

Epimerase (Msed_0639) and Mutase (Msed_0638 and Msed_2055) Convert ( S )-Methylmalonyl-Coenzyme A (CoA) to Succinyl-CoA in the Metallosphaera sedula 3-Hydroxypropionate/4-Hydroxybutyrate Cycle

“…Of interest here are the identity and biochemical properties of the methylmalonylCoA epimerase and methylmalonyl-CoA mutase in the M. sedula 3-HP/4-HB cycle. Versions of these two enzymes have been identified in the genomes of bacteria (2, 34, 37-39, 43, 52, 56), animals (13,20,33,53,55), and algae (47), as well as in archaea (14), but have not been implicated in CO 2 fixation pathways. Previous studies on MCEs and MCMs showed that these enzymes catalyze the reversible conversion of (S)-methylmalonyl-CoA to succinylCoA, which is a key intermediate in the tricarboxylic acid cycle.…”