Abstract
Ceramidases (CDase) are enzymes that catalyze the hydrolysis of N-acyl linkage of ceramide (Cer) to generate sphingosine and free fatty acids. In this study we report the purification and characterization of a novel second type of neutral ceramidase from rat brain (RBCDase II). Triton X-100 protein extract from rat brain membrane was purified sequentially using Q-Sepharose, HiLoad16/60 Superdex 200
pg, heparin-Sepharose, phenyl-Sepharose HP, and Mono Q columns. After Mono Q, the specific activity of the enzyme increased by ~
15,000-fold over that of the rat brain homogenate. This enzyme has pH optima of 7.5, and it has a larger apparent molecular weight (110
kDa) than the previously purified (90
kDa) and characterized neutral rat brain CDase (RBCDase I). De-glycosylation experiments show that the differences in molecular mass of RBCDase I and II on SDS-PAGE are not due to the heterogeneity with N-glycan. RBCDase II is partially stimulated by Ca
2+ and is inhibited by pyrimidine mono nucleotides such as TMP and UMP. This finding is significant as it demonstrates for the first time an effect by nucleotides on a CDase activity. The enzyme was also inhibited by both oxidized and reduced GSH. The effects of metal ions were examined, and we found that the enzyme is very sensitive to Hg
2+ and Fe
3+, while it is not affected by Mn
2+. EDTA was somewhat inhibitory at a 20
mM concentration.
► Purified a second more hydrophobic type of nCDase (RBCDase II) from rat brain. ► Characterized many biochemical properties of the RBCDase II. ► The purified RBCDase II is different from those reported data of RBCDase I in several aspects.