The Influence of Specific Phospholipids on the Interaction of Hexokinase with the Outer Mitochondrial Membrane

Abstract

Repeated washing of a brain mitochondrial fraction results in a progressive decrease in the proportion of mitochondrially bound hexokinase that can be solubilized during a subsequent incubation with glucose-6-phosphate (glucose-6-P). Phospholipids removed during the washing procedure can be added back to washed mitochondria, resulting in enhancement of the solubilization by glucose-6-P. Column and thin-layer chromatographic methods have been used to isolate and identify active phospholipids. Additional studies were performed with purified lipids obtained commercially. Both lysophospholipids and acidic phospholipids were active in enhancing solubilization of hexokinase by glucose-6-P. Phospho-inositides, particularly diphosphoinositide, were quite effective, raising the possibility that the actively metabolized phosphoinositides may be involved in regulation of hexokinase binding in vivo.

Binding of non-catalytic ATP to human hexokinase I highlights the structural components for enzyme–membrane association control

“…Such a structural localization of positively charged residues surrounding the nucleotide binding site, all belonging to the N-terminal domain, supports the hypothesis of a membrane interface location for this molecular region, which would stabilize the interaction between HK-I and the mitochondrion through the establishment of ionic interactions with the membrane phospholipid phosphate heads. Indeed, binding of the enzyme is influenced by the phospholipidic composition of the membrane [33].…”