Biochemical and structural characterization of tomato polyphenol oxidases provide novel insights into their substrate specificity.

ABSTRACT: Polyphenol oxidases (PPOs) contain the structurally similar enzymes tyrosinases (TYRs) and catechol oxidases (COs). Two cDNAs encoding pro-PPOs from tomato (Solanum lycopersicum) were cloned and heterologously expressed in Escherichia coli. The two pro-PPOs (SlPPO1-2) differ remarkably in their activity as SlPPO1 reacts with the monophenols tyramine (k_cat = 7.94 s^-1) and phloretin (k_cat = 2.42 s^-1) and was thus characterized as TYR, whereas SlPPO2 accepts only diphenolic substrates like dopamine (k_cat = 1.99 s^-1) and caffeic acid (k_cat = 20.33 s^-1) rendering this enzyme a CO. This study, for the first time, characterizes a plant TYR and CO originating from the same organism. Moreover, X-ray structure an

SUBMITTER: Kampatsikas I 

PROVIDER: S-EPMC6411738 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature