The phenyl propanoid pathway enzymes in Solanum tuberosum exist as a multienzyme complex

The elution profile of the core sequence enzymes of the phenyl propanoid pathway, namely phenyl alanine ammonia lyase, t-cinnamic acid 4-hydroxylase and p-coumaryl CoA ligase, on AcA 34 column suggested the existence of a high molecular form (P1) and a low molecular form (P2) for all the three enzymes. All the P1 forms eluted together in same fractions, while the P2 forms eluted out according to their respective molecular mass. Rechromatography of P1 form under identical conditions showed a similar elution profile (Q1 and Q2 forms). Further, the Q1 form did not show any significant increase in specific activity when compared to the P1 form. These results suggested the possibility of these enzymes existing as a protein cluster. Further confirmation was obtained on repeated column chromatography of the Q1 form in presence of 0.1 M KCl which did not result in complete dissociation of the complex to its individual enzyme components. The identification of the subunit polypeptide of the individual enzyme components in the multi enzyme complex and the in vitro demonstration of the phenyl propanoid core pathway reaction sequence using phenylalanine alone as a substrate supplementing the required cofactors for appropriate reactions substantiated that at least the core enzymes of the phenyl propanoid sequence existed as a multi enzyme complex.