1.7.2.1	nitrite reductase (NO-forming)	nitrifier denitrification	-	
1.7.2.4	nitrous-oxide reductase	nitrifier denitrification	-	
1.7.2.5	nitric oxide reductase (cytochrome c)	nitrifier denitrification	-	
1.7.2.9	hydroxylamine oxidase	nitrifier denitrification	-