Sphingomyelinase (SMase) activity was measured in Entamoeba histolytica particulate and soluble subcellular fractions. The effects on SMase of incubation time, total protein concentration, pH, and several divalent cations were determined. SMase-C and other unidentified esterase activity were detected in soluble and particulate fractions. SMase-C was 94.5-96.0% higher than the unidentified esterase activity. Soluble and insoluble SMase-C specific activities increased with protein dose and incubation time. Soluble and insoluble SMase-C activities were maximum at pH 7.5 and were dependent on Mg 2+, Mn 2+, or Co 2+, and inhibited by Zn 2+, Hg 2+, Ca 2+, and EDTA. SMase-C was active in the pH range of 3-10 and its maximum activity was at pH 7.5. The soluble and insoluble SMases have remarkably similar physicochemical properties, strongly suggesting that E. histolytica has just one isoform of neutral SMase-C that had not been described before and might be essential for E. histolytica metabolism or virulence.
Bibliographical noteFunding Information:
The authors thank Antonio Luna de la Rosa for the artwork. This study was supported by FIS/IMSS/PROT/509 and CONACyT/80049/FIS/IMSS/PROT/600.
Copyright 2010 Elsevier B.V., All rights reserved.
All Science Journal Classification (ASJC) codes
- Infectious Diseases