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Properties and Activity Changes of Chlorogenic Acid:Glucaric Acid Caffeoyltransferase From Tomato (Lycopersicon

D Strack¹, W Gross

¹Institut für Pharmazeutische Biologie der Technischen Universität Braunschweig, Mendelssohnstrasse 1, D-3300 Braunschweig, Federal Republic of Germany.

Plant Physiology

|January 1, 1990

Summary

Researchers purified a novel tomato enzyme that transfers caffeic acid to glucaric and galactaric acids, preferring glucaric acid. This enzyme, chlorogenic acid:glucaric acid O-caffeoyltransferase, shows sequential activity during tomato seedling development.

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Area of Science:

Biochemistry
Plant Science
Enzymology

Background:

Acyltransferases play crucial roles in plant secondary metabolism.
Tomato (Lycopersicon esculentum Mill.) cotyledons are a source of novel enzymes involved in esterification.
Understanding caffeic acid transfer is key to elucidating plant metabolic pathways.

Purpose of the Study:

To purify and characterize a novel acyltransferase from tomato cotyledons.
To investigate the enzyme's substrate specificity and kinetic properties.
To determine the enzyme's role in the formation of caffeoyl esters of glucaric and galactaric acids.

Main Methods:

Purification of the acyltransferase using ammonium sulfate precipitation and ion-exchange chromatography.
Enzyme activity assays using chlorogenic acid as the acyl donor and glucaric/galactaric acids as acceptors.
Determination of kinetic parameters (K(m), V(max)) and optimal reaction conditions (pH, temperature).
Analysis of enzyme molecular weight via SDS-PAGE and gel filtration.

Main Results:

A novel acyltransferase was purified with 2400-fold enrichment, catalyzing caffeic acid transfer from chlorogenic acid to glucaric and galactaric acids.
The enzyme exhibited specific activities of 625 nkat (caffeoylglucaric acid) and 310 nkat (caffeoylgalactaric acid).
Optimal activity was observed at pH 5.7 and 38°C, with apparent K(m) values of 0.4 mM for glucaric acid and 1.7 mM for galactaric acid, indicating a preference for glucaric acid.

Conclusions:

A single enzyme, proposed as chlorogenic acid:glucaric acid O-caffeoyltransferase (EC 2.3.1.-), is responsible for both glucaric and galactaric acid ester formation.
The enzyme's activity and related preceding enzymes show sequential changes during tomato seedling development.
This enzyme plays a significant role in the biosynthesis of specific caffeoyl esters in tomato plants.