Figure 1: Proposed pathways (route a-f) for the catabolism of phenylacetic acid (PA) and 4-hydroxyphenylacetic acid (4-HPA) in different microorganisms. Route d is referred as ‘aerobic hybrid pathway’ [2]. Abbreviations: PhAc-CoA, Phenylacetyl-CoA; 2-HPA, 2-hydroxyphenylacetic acid; 3-HPA, 3-hydroxyphenylacetic acid; 3,4-DHPA, 3,4-dihydroxyphenylacetic acid; 2,5-DHPA, 2,5-dihydroxyphenylacetic acid; 3,4-DHB, 3,4-dihydroxybenzaldehyde. Broken arrows indicate multiple steps. Steps involving incorporation of molecular oxygen are indicated. Symbol ‘?’ indicate hypothetical route for PA metabolism.