The degradative pathway of the s-triazine melamine. The steps to ring cleavage

Abstract

1. The degradative pathway of melamine (1,3,5-triazine-2,4,6-triamine) was examined in Pseudomonas sp. strain A. 2. The bacterium grew with melamine, ammeline, ammelide, cyanuric acid or NH+4 as sole source of nitrogen, and each substrate was entirely metabolized. Utilization of ammeline, ammelide, cyanuric acid or NH+4 was concomitant with growth. But with melamine as substrate, a transient intermediate was detected, which was identified as ammeline by three methods. 3. Enzymes from strain A were separated by chromatography on DEAE-cellulose, and four activities were examined. 4. Melamine was converted stoichiometrically into equimolar amounts of ammeline and NH+4. 5. Ammeline was converted stoichiometrically into equimolar amounts of ammelide and NH+4; ammelide was identified by four methods. 6. Ammelide was converted stoichiometrically into equimolar amounts of cyanuric acid and NH+4; cyanuric acid was identified by four methods. 7. Cyanuric acid was converted by an enzyme preparation into an unidentified product with negligible release of NH+4. 8. The specific activities of the degradative enzymes (greater than or equal to 0.3 mkat/kg of protein) were high enough to explain the growth rate of the organism. 9. The bacterium converted 0.4 mM-melamine anaerobically into 2.3 mM-NH+4. 10. Two other pseudomonads and two strains of Klebsiella pneumoniae were also examined, with similar results. 11. The degradative pathway of melamine appears to be hydrolytic, and proceeds by three successive deaminations to cyanuric acid, which is further metabolized.

Anaerobic dechlorination of tetrachloromethane and 1,2-dichloroethane to degradable products by pure cultures of Desulfobacterium sp. and Methanobacterium sp.

“…Chlorinated hydrocarbons, methane and ethene were determined after separation on packed columns in a GC equipped with FID [23]. A Porapak P column was used routinely [7] and Durapak [24], Chromosorb 101 [24] and Tenax [7] columns were used to confirm the identity of each product by co-chromatography with authentic material.…”

An unexpected vestigial protein complex reveals the evolutionary origins of an s-triazine catabolic enzyme

“…cyanuric acid). Interestingly, many of the striazine catabolic pathways that have evolved share a common structure, in which specific 'upper pathways' convert different s-triazines to cyanuric acid (1,3,5-triazine-2,4,6-triol) by hydrolosis of the three substituents that decorate the heterocyclic ring (3)(4)(5). A common 'lower pathway' then mineralizes cyanuric acid to carbon dioxide and ammonia.…”

Cloning and comparison of the DNA encoding ammelide aminohydrolase and cyanuric acid amidohydrolase from three s-triazine-degrading bacterial strains

“…strain NRRLB-12227 metabolizes melamine (1,3,5-triazine-2,4,6-triamine) by a six-step pathway through ammeline, ammelide, cyanuric acid, biuret, and urea ( Fig. 1) (3,8,9). Pseudomonas sp.…”