title: Mechanism of xanthine oxidase catalyzed biotransformation of HMX under anaerobic conditions.
abstract: Enzyme catalyzed biotransformation of the energetic chemical octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is not known. The present study describes a xanthine oxidase (XO) catalyzed biotransformation of HMX to provide insight into the biodegradation pathway of this energetic chemical. The rates of biotransformation under aerobic and anaerobic conditions were 1.6+/-0.2 and 10.5+/-0.9 nmolh(-1)mgprotein(-1), respectively, indicating that anaerobic conditions favored the reaction. The biotransformation rate was about 6-fold higher using NADH as an electron-donor compared to xanthine. During the course of reaction, the products obtained were nitrite (NO(2)(-)), methylenedinitramine (MDNA), 4-nitro-2,4-diazabutanal (NDAB), formaldehyde (HCHO), nitrous oxide (N(2)O), formic acid (HCOOH), and ammonium (NH(4)(+)). The product distribution gave carbon and nitrogen mass-balances of 91% and 88%, respectively. A comparative study with native-, deflavo-, and desulfo-XO and the site-specific inhibition studies showed that HMX biotransformation occurred at the FAD-site of XO. Nitrite stoichiometry revealed that an initial single N-denitration step was sufficient for the spontaneous decomposition of HMX.
authors.affiliation: Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Avenue, Que., Montreal, Canada H4P 2R2.
authors.forename: Bharat
authors.initials: B
authors.lastname: Bhushan
authors.forename: Louise
authors.initials: L
authors.lastname: Paquet
authors.forename: Annamaria
authors.initials: A
authors.lastname: Halasz
authors.forename: Jim C
authors.initials: JC
authors.lastname: Spain
authors.forename: Jalal
authors.initials: J
authors.lastname: Hawari
mesh_terms: D001392:Azocines / Q000378:metabolism*; D002244:Carbon / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004583:Electrons; D005557:Formaldehyde / Q000737:chemistry; D005561:Formates / Q000737:chemistry; D006573:Heterocyclic Compounds, 1-Ring / Q000378:metabolism*; D006838:Hydrocarbons; D006863:Hydrogen-Ion Concentration; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical; D009243:NAD / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000737:chemistry; D009609:Nitrous Oxide / Q000737:chemistry; D010655:Phenylenediamines / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014969:Xanthine Oxidase / Q000378:metabolism*
chemical_list: D001392:Azocines; D005561:Formates; D006573:Heterocyclic Compounds, 1-Ring; D006838:Hydrocarbons; D009573:Nitrites; D010655:Phenylenediamines; D000644:Quaternary Ammonium Compounds; D009243:NAD; C030544:formic acid; D005557:Formaldehyde; C030011:carbene; D002244:Carbon; D014969:Xanthine Oxidase; D009609:Nitrous Oxide; C007950:octogen; D009584:Nitrogen; D008697:Methane; C002049:dinitramine