Biochemical characterization of elongase activity in corn (Zea mays L.) roots

Chemical analysis of 4-day-old corn (Zea mays L.) root cell walls revealed that the lipophilic biopolymer suberin forms an important constituent of rhizodermal and hypodermal cell walls. Identified aliphatic monomers had chain lengths ranging from C-16 to C-26 and they belonged to 5 substance classes (omega-hydroxycarboxylic acids, 1,omega-dicarboxylic acids, 2-hydroxycarboxylic acids, carboxylic acids and alcohols) by which suberin is characterized. Biochemical experiments proved the occurrence of elongase activities in corn roots. Highest enzymatic activities were found in corn root microsomes, and major products synthesized by root elongases were elongated fatty acids with chain lengths ranging from C-20 to C-24. Preferred substrates of root elongases were acyl-CoAs of the chain length C-18 and C-20, whereas monounsaturated acyl-CoAs (C-16:1 and C-18:1) and acyl-CoAs of lower (C-12-C-16) and higher chain lengths (C-22-C-24) were rarely elongated. Elongase activities significantly decreased over the length (40 cm) of 10-day-old corn roots going from the young tip to the older base of the root. Thus, results presented here show the presence and activity of elongases in roots of plants. (C) 2004 Elsevier Ltd. All rights reserved.