Structural Aspects of Citrate Biochemistry

Abstract

Publisher Summary This chapter discusses the structural aspects of citrate biochemistry. The citrate ion is distributed throughout the human body and takes part in the all-important tricarboxylic acid (Krebs) cycle. The citrate ion is simple, just a backbone of five carbon atoms with carboxyl groups at C-1, C-3, and C-5 and an additional hydroxyl group on the central carbon atom, C-3. This backbone, studied in many crystal structures, can be fully extended, or one or both of the terminal carboxyl groups may be swung around, possibly forming a hydrogen bond to the central carboxyl group. For citrates studied in the crystalline state, it is found that the central carboxyl group and its adjacent hydroxyl group lie approximately in a plane perpendicular to the plane of the zigzag of the five-carbon backbone. One reason that the α-hydroxycarboxylate group is nearly planar may be its powerful chelating ability. Grenerally, this group with a bite of 2.56 A, binds metal ions. In the absence of a metal ion available to bind to this group, a hydrogen atom may bind in this place.