Premium
Structural and kinetic studies on adenylosuccinate lyase from Mycobacterium smegmatis and Mycobacterium tuberculosis provide new insights on the catalytic residues of the enzyme
Author(s) -
Banerjee Sanchari,
Agrawal Monika J.,
Mishra Diptimayee,
Sharan Siddharth,
Balaram Hemalatha,
Savithri Handanhal S.,
Murthy Mathur R. N.
Publication year - 2014
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.12730
Subject(s) - mycobacterium smegmatis , biochemistry , active site , lyase , mycobacterium tuberculosis , threonine , enzyme , biology , mycobacterium , stereochemistry , chemistry , bacteria , serine , tuberculosis , genetics , medicine , pathology
Adenylosuccinate lyase ( ASL ), an enzyme involved in purine biosynthesis, has been recognized as a drug target against microbial infections. In the present study, ASL from Mycobacterium smegmatis ( Ms ASL ) and Mycobacterium tuberculosis ( Mtb ASL ) were cloned, purified and crystallized. The X‐ray crystal structure of Ms ASL was determined at a resolution of 2.16 Å. It is the first report of an apo‐ ASL structure with a partially ordered active site C3 loop. Diffracting crystals of Mtb ASL could not be obtained and a model for its structure was derived using Ms ASL as a template. These structures suggest that His149 and either Lys285 or Ser279 of Ms ASL are the residues most likely to function as the catalytic acid and base, respectively. Most of the active site residues were found to be conserved, with the exception of Ser148 and Gly319 of Ms ASL . Ser148 is structurally equivalent to a threonine in most other ASL s. Gly319 is replaced by an arginine residue in most ASL s. The two enzymes were catalytically much less active compared to ASL s from other organisms. Arg319Gly substitution and reduced flexibility of the C3 loop might account for the low catalytic activity of mycobacterial ASL s. The low activity is consistent with the slow growth rate of Mycobacteria and their high GC containing genomes, as well as their dependence on other salvage pathways for the supply of purine nucleotides. Structured digital abstractpurB and purB bind by x-ray crystallography ( View interaction )