Document Detail

Characterization of an aldolase-dehydrogenase complex from the cholesterol degradation pathway of Mycobacterium tuberculosis.
MedLine Citation:
PMID:  23614353     Owner:  NLM     Status:  Publisher    
HsaF and HsaG are an aldolase and dehydrogenase from the cholesterol degradation pathway of M. tuberculosis. HsaF could be heterologously expressed and purified as a soluble dimer, but the enzyme was inactive in the absence of HsaG. HsaF catalyzes the aldol cleavage of 4-hydroxy-2-oxoacids to produce pyruvate and an aldehyde. The enzyme requires divalent metals for activity, with a preference for Mn2+. The Km values for 4-hydroxy-2-oxoacids were about 20-fold lower than observed for the aldolase homologue, BphI from the polychlorinated biphenyl degradation pathway. Acetaldehyde and propionaldehyde were channeled directly to the dehydrogenase, HsaG, without export to the bulk solvent where they were transformed to acyl-CoA in an NAD+ and coenzyme A dependent reaction. HsaG is able to utilize aldehydes up to five carbons in length as substrates, with similar catalytic efficiencies. The HsaF-HsaG complex was crystallized and its structure determined to a resolution of 1.93 Å. Substitution of Serine 41 in HsaG with isoleucine or aspartate resulted in about 35-fold increase in Km for CoA but only 4-fold increase in Km dephospho-CoA, suggesting that this residue interacts with the 3'-ribose phosphate of CoA. A second protein annotated as a 4-hydroxy-2-oxopentanoic acid aldolase in Mycobacterium tuberculosis (MhpE, Rv3469c) was expressed and purified, but was found to lack aldolase activity. Instead this enzyme was found to possess oxaloacetate decarboxylase activity, consistent with the conservation (with the 4-hydroxy-2-oxoacid aldolases) of residues involved in pyruvate enolate stabilization.
Jason Carere; Sarah E McKenna; Matthew S Kimber; Stephen Y K Seah
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-4-24
Journal Detail:
Title:  Biochemistry     Volume:  -     ISSN:  1520-4995     ISO Abbreviation:  Biochemistry     Publication Date:  2013 Apr 
Date Detail:
Created Date:  2013-4-25     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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