Purification and characterization of the heat-stable factors essential for the conversion of lignoceric acid to cerebronic acid and glutamic acid: identification of N-acetyl-L-aspartic acid.

The conversion of lignoceric acid to cerebronic acid, ceramides, cerebrosides, and glutamic acid is catalyzed by a rat brain particulate preparation. The heat-stable factor, prepared from calf cerebellum, together with the heat-labile factor, a pyridine nucleotide, and Mg2+ are essential to all of these metabolic pathways. Our previous work showed that the heat-stable factor is composed of at least two components, HSF-1 and HSF-2, and identified HSF-2 as D-glucose-6-phosphate. In the current investigation, HSF-1 was further purified and found to be N-acetyl-L-aspartic acid. In addition, it was discovered that a third component, HSF-3, is also required for heat-stable factor activity. A reconstituted system composed of N-acetylaspartic acid, glucose-6-phosphate, and HSF-3 fully replaced the heat-stable factor essential for the conversion of lignoceric acid to cerebronic acid and glutamic acid. The reconstituted heat-stable factor did not show the initial time lag always observed with the crude heat-stable factor.