2Department of Pharmaceutical Chemistry, Himalayan Pharmacy Institute, Majhitar, Rangpo, Sikkim 737136, India; fax: 03592-246462; E-mail: email@example.com
3Department of Pharmacognosy, P. E. S. College of Pharmacy, Hanumanthnagar, Bangalore 560050, India; fax: 080-26507428; E-mail: firstname.lastname@example.org
* To whom correspondence should be addressed.
Received January 9, 2009; Revision received February 26, 2009
The activities of inorganic pyrophosphatase (PPase) and adenosine triphosphatase (ATPase) were studied in the plasma membrane of Leishmania donovani promastigotes and amastigotes. It was shown that the specific activity of PPase was greater than that of ATPase in the promastigote plasma membrane. We characterized H+-PPase present in the plasma membrane of L. donovani and investigated its possible role in the survival of promastigote and amastigote. PPase activity was stimulated by K+ and sodium orthovanadate and inhibited by pyrophosphate analogs (imidodiphosphate and alendronate), KF, N,N′-dicyclohexylcarbodiimide (DCCD), thiol reagents (p-chloromercuribenzenesulfonate (PCMBS), N-ethylmaleimide (NEM), and phenylarsine oxide (PAO)), the ABC superfamily transport modulator verapamil, and also by the F1Fo-ATPase inhibitor quercetin. ATPase activity was stimulated by K+ and verapamil, inhibited by DCCD, PCMBS, NEM, sodium azide, sodium orthovanadate, and quercetin, and was unaffected by PAO. We conclude that there are significant differences within promastigote, amastigote, and mammalian host in cytosolic pH homeostasis to merit the inclusion of PPase transporter as a putative target for rational drug design.
KEY WORDS: Leishmania donovani promastigote and amastigote, pyrophosphatase, ATPase, plasma membrane, imidodiphosphate, verapamil