Vol 27 No 2 December - The Indian Society for Parasitology

Journal of Parasitic Diseases
Vol. 27 (2) Dec. 2003, pp. 119-123
Effect of Dextran and Polyvinylpyrrolidone
on the activity of enzymes released
extracellulary by Trypanosoma brucei
UKPONG I.G.**, OPARA K.N.*
Department of Zoology, University of Ibadan,**
Department of Zoology, University of Uyo, Nigeria*
Trypanosoma brucei releases the enzymes acid phosphatase and peptidase extracellularly into
phosphate/saline/glucose (PSG) pH 8.0 buffer, in which the organism is incubated in vitro at 4°c for 5-30
minutes with lysosomotropic compounds dextran and polyvinylpyrrolidone (PVP). The effect of these
compounds was evaluated on the activity of the two enzymes. Both compounds promoted a time-dependent
release of acid phosphatase but inhibited the release of the peptidase. While dextran had no lethal effect on
the survival of the trypanosomes after 30 minutes of incubation, PVP killed most of the parasites after 15
minutes of exposure.
Key words : Acid Phosphatase, Dextran, Enzyme Release, Peptidase, Proteases, PVP, Trypanosoma brucei
INTRODUCTION
platelet aggregation, blood coagulation and
thrombocytopaenia (Nwagwu et al., 1989; Davis et al.,
rypanosomes are flagellated protozoan parasites
1974). Considering the importance of endocytosis-
Tof medical and veterinary importance. In man and
exocytosis in trypanosomes, inhibiting or inducing
domestic animals they exhibit varying degree of
these processes would be a step in the right direction
pathogenicity. Chemotherapy is still regarded as the
towards the development of effective chemomost
promising approach to the treatment and control
therapeutic agents and/or vaccines against
of African trypanosomiasis. Endocytosis-Exocytosis
trypanosomiasis. We had, previously shown that the
is a cellular process that occurs widely in eukaryotic
released proteases include proteolytic bands of Mr
cells. It involves sequential formation and fusion of
200, 106, 93, 63, 48, 40 and 25 KDa among which are
membrane-bound vesicles, during which time, the
cysteine and trypsin-like serine proteases as well as
macromolecules involved are sequestered or
acid phosphatase (Okenu and Opara 1996; Ekpo et al.,
compartmentalized in vesicles. This is an important
1996 and Steiger et al, 1980). We have also
feature that facilitates direct transfer of substances
demonstrated that lysosomotropic drugs such as
between the outer and inner cell environment chloroquine, retinal, swainsonine, dextran and
(Silverstain et al., 1989' Blumenthal 1987; Albert et
polyvinylpyrrolidone (PVP) inhibit or activate the
al., 1989).
release of these enzymes (Opara et al., 1994; Opara
The processes of endocytosis-exocytosis occur and Okenu 1996). In this report we have evaluated the
through the flagellar pocket in many species of effect of the uptake of dextran and PVP on the survival
trypanosomes (Opperdoes et al., 1987; Langreth and of trypanosomes and the effect of these compounds on
Balber 1975) for the secretion of proteases and nutrient the activity of two of the enzymes released by T. brucei
uptake (Knowles et al., 1987; Nwagwu et al., 1988; namely acid phosphatase and peptidase.
Huet et al., 1992, Webster and Marsh 1986; Okenu and
Opara, 1996). The released protease(s) have been
MATERIALS AND METHODS
implicated in the pathology of the disease such as Fluorogenic peptide substrates with a carboxyl-
terminal 7-amino-4-trifluoromethyl Coumarin (AFC)
* Corresponding Author
were purchased from Enzyme Systems Product
Livermore, Ca, (USA) while 4-methylumbelliferyl