title: Study of mechanism of interaction of truncated isoniazid-nicotinamide adenine dinucleotide adduct against multiple enzymes of Mycobacterium tuberculosis by a computational approach.
abstract: OBJECTIVE
  Isoniazid (INH) is one of the effective antituberculosis (TB) drugs used for TB treatment. However, most of the drug-resistant Mycobacterium tuberculosis (MTB) clinical strains are resistant to INH, a first-line antituberculous drug. Certain metabolic enzymes such as adenosylhomocysteinase (Rv3248c), universal stress protein (Rv2623), nicotinamide adenine dinucleotide (reduced)-dependent enoyl-acyl carrier protein reductase (Rv1484), oxidoreductase (Rv2971), dihydrofolate reductase (Rv2763c), pyrroline-5-carboxylate dehydrogenase (Rv1187) have been identified to bind INH-nicotinamide adenine dinucleotide (INH-NAD) and INH-nicotinamide adenine dinucleotide phosphate adducts coupled to Sepharose resin. These enzymes are reported to be involved in many important biochemical processes of MTB, including cysteine and methionine metabolism, mycobacterial growth regulation, mycolic acid biosynthesis, detoxification of toxic metabolites, folate biosynthesis, etc. The truncated INH-nicotinamide adenine dinucleotide (oxidized) adduct, 4-isonicotinoylnicotinamide, isolated from urine samples of human TB patients treated with INH therapy is proposed to have antimycobacterial activity.
  
  
  METHODS
  To understand the mechanism of interaction of the truncated INH-NAD adduct, binding energy studies were carried out on the aforementioned six enzymes with known three-dimensional structures using AutoDock4.2.
  
  
  RESULTS
  In silico docking analysis of these MTB enzymes with the truncated INH-NAD adduct showed favorable binding interactions with docking energies ranging from -5.29 to -7.07 kcal/mol.
  
  
  CONCLUSIONS
  Thus, in silico docking study revealed that the INH-NAD adduct, which is generated in vivo after INH activation, may undergo spontaneous hydrolysis to form the truncated INH-NAD adduct and further binds and inhibits multiple enzymes of MTB, in addition to InhA, confirming that INH is an effective anti-TB drug acting at multiple enzymes. Further analysis of amino acid residues in the active site of INH-NAD-binding proteins showed the probable presence of catalytic triad in four enzymes possibly involved in INH binding to the enzyme.
authors.affiliation: Bioinformatics Centre, Biochemistry and JB Tropical Disease Research Centre, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Maharashtra, India.
authors.forename: Lingaraja
authors.initials: L
authors.lastname: Jena
authors.affiliation: Bioinformatics Centre, Biochemistry and JB Tropical Disease Research Centre, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Maharashtra, India.
authors.forename: Shraddha
authors.initials: S
authors.lastname: Deshmukh
authors.affiliation: Bioinformatics Centre, Biochemistry and JB Tropical Disease Research Centre, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Maharashtra, India.
authors.forename: Pranita
authors.initials: P
authors.lastname: Waghmare
authors.affiliation: Bioinformatics Centre, Biochemistry and JB Tropical Disease Research Centre, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Maharashtra, India.
authors.forename: Satish
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Bioinformatics Centre, Biochemistry and JB Tropical Disease Research Centre, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Maharashtra, India. Electronic address: bc_harinath@yahoo.com.
authors.forename: Bhaskar C
authors.initials: BC
authors.lastname: Harinath
mesh_terms: D000995:Antitubercular Agents / Q000737:chemistry* / Q000378:metabolism; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007538:Isoniazid / Q000737:chemistry* / Q000378:metabolism; D062105:Molecular Docking Simulation; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000201:enzymology*; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D014376:Tuberculosis / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D009243:NAD; D007538:Isoniazid
keywords: Catalytic triad; Docking; Isoniazid; Truncated INH–NAD adduct