Table 2.

Characteristics of functional processes for the degradation of HMW PAHs

Parameter	Characteristics of:
	RCP	SCP	CAP
Input	(HMW) PAHs	Ring cleavage compounds	Protocatechuate
Output	Ring cleavage compounds	Pyruvate	Acetyl-CoA/succinyl-CoA
		Metabolites acceptable to RCP
Metabolite centric	Relatively highly branched pathways	Linear or less branched pathways	Partial RCP and SCP
	High-degree metabolites	Low-degree metabolites	Linear pathway
	Gradual increase in MW	Gradual decrease in MW
Enzyme centric	O2dependent	Productive	Productive
	Non-productive metabolites	Constitutively/loosely regulated	Constitutive expression
	Tightly regulated	Generally broad substrate specificities	Entering TCA cycle
	Diverse substrate specificity	Preparative for RCP or CAP	Belong to EC 1-5
	Pathway determining	Belong to EC 1-5
	Preparative for SCP
	Mostly belong to EC 1