Recombinant Mycobacterium avium Malate dehydrogenase (mdh)
Description
Biochemical Role of MDH in Mycobacteria
Malate dehydrogenase (MDH; EC 1.1.1.37) catalyzes the reversible NAD(H)-dependent oxidation of malate to oxaloacetate, a key step in the tricarboxylic acid (TCA) cycle. In mycobacteria, MDH supports both energy production and redox balance, particularly under varying environmental conditions . Phosphorylation by serine/threonine protein kinases (STPKs) regulates MDH activity; for example, Mycobacterium tuberculosis MDH phosphorylation on threonine residues inhibits enzymatic function, impacting metabolic adaptation during hypoxia .
Recombinant MDH Production and Characterization
Recombinant MDH is typically expressed in Escherichia coli systems for functional studies. While M. avium-specific MDH data are sparse, protocols for related species like M. tuberculosis and M. ulcerans inform production methods :
In M. smegmatis, MDH absence leads to malate accumulation and growth defects, highlighting its non-redundant role in oxidative metabolism . Heterologous expression of M. tuberculosis MDH rescues these defects, suggesting functional conservation across species .
Immune Recognition and Epitope Mapping
Monoclonal antibodies (mAbs) against M. avium proteins reveal cross-reactivity patterns with MDH-related antigens. Key findings include:
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GroEL2 (MAP_3936): A chaperone targeted by mAbs 7A6, 11F8, and 10C12, with epitopes localized to central and C-terminal regions .
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Acetyl-CoA carboxylase (MAP_3404): Five mAbs bind distinct epitopes, including a linear epitope (residues 316–330) .
Though MDH itself is not directly listed in M. avium antigen tables, phosphorylation studies in M. tuberculosis suggest MDH interacts with FHA domain-containing proteins like GarA, modulating metabolic pathways .
Functional Redundancy with MQO
Malate:quinone oxidoreductase (MQO) often coexists with MDH in mycobacteria. Key comparisons:
In M. avium, this redundancy may enable metabolic flexibility under nutrient stress, though direct evidence remains unexplored.
Research Applications and Challenges
Recombinant MDH is pivotal for:
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Drug target validation: Phosphorylation sites (e.g., Thr residues) offer targets for kinase inhibitors .
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Diagnostic tools: Cross-reactive mAbs against conserved epitopes could aid in TB/MAIC serodiagnostics .
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Metabolic engineering: Optimizing TCA flux in synthetic biology platforms .
Challenges include low yields in recombinant expression and species-specific functional divergence .
Product Specs
Target Background
KEGG: mav:MAV_1380
