Trypanosoma evansi sialidase: surface localization,properties and hydrolysis of ghost red blood cells and brain cells-implications in trypanosomiasis

A membrane-bound sialidase was isolated from blood stream (BS) Trypanosoma evansi partially purified and characterized. The enzyme is a glycosyl phosphatidyl inositol (GPI) membrane anchored protein. It was solubilized from T. evansi cells recovered from infected camel blood by detergent treatment with Triton CF 54 and partially purified by a series of chromatography steps. The enzyme was optimally active at pH 5.5 and 37 degrees C. It had a KM and Vmax values of 4.8 x 10(-6) M and 3.75 x 10(-6) mol/min x mg protein with Neu5Acalpha2, 3lac as substrate respectively. The KM and Vmax values with fetuin (4-nitrophenyl-oxamic acid) as substrate were 2.9 x 10(-2) M and 4.2 x 10(-3) mol/min x mg protein in the same respect. Kinetic analysis with methly umbelliferyl sialate (MU-Neu5Ac) gave KM and Vmax values of 0.17 mM and 0.84 mmol/min x mg protein respectively. The T. evansi SD could hydrolyse internally linked sialic acid residues of the ganglioside GM2, but was inactive towards colomic acid, and NeuSAc2, 6. lac. When ghost red blood cell (RBC) was used as substrate, it desialylated the RBC in the following order of efficiency; mouse, rat, camel, goat, and dog. Similarly, cerebral cells isolated from BalbC mouse was desialylated by the T. evansi SD. Inhibition studies using 2-deoxy-2, 3 didehydro-N-acetyl neuraminic acid (NeuAc2, 3en) against MU-Neu5Ac revealed a competitive inhibition pattern with Ki of 5.8 microM. The enzyme was also inhibited non-competitively by parahydroxy oxamic acid (pHOA), and competitively by N-ethylmaleimide and N-bromosuccinate with Ki values of 25, 42, and 53 microM, respectively. It was activated by Mg2+ ion and inhibited by Cu2+ and Zn2+.     

Camel and Horse Milk Casein Hydrolysates Exhibit Angiotensin Converting Enzyme Inhibitory and Antioxidative Effects In Vitro and In Silico

International Journal of Peptide Research and Therapeutics - Angiotensin converting enzyme (ACE) and reactive oxygen species are crucial targets for nutritional management of hypertension. The aim...     

Schistosomiasis: Evaluation of the indirect fluorescent antibody,complement fixation,and slide flocculation tests in screening for schistosomiasis

Foreign Service personnel undergo pertinent parasitologic examinations upon return from foreign duty posts. Under this program, 2800 sera have been evaluated for schistosomiasis in this laboratory. The majority of individuals tested were considered to have limited exposure to schistosomiasis, although a few indigenous people from endemic areas also were screened. Nonindigenous populations usually gave stronger serological reactions than did indigenous populations. A comparison was made between those having protozoan and helminthic infections and those that were negative parasitologically. A number of subjects with tissue-phase helminths were evaluated and consistently gave strong reactions in the indirect fluorescent antibody (IFA) tests. On the other hand, there was no characteristic pattern observed in individuals with low serum titers. The IFA test proved to be highly sensitive and sufficiently specific for screening, provided that low background reactions were disregarded (i.e., when +/? and 1+ reactions were ignored at low serum dilutions). Thus, the IFA test was the method of choice for screening. Recourse to the complement fixation (CF) and slide flocculation (SF) tests, however, was necessary for definitive diagnosis. In view of the differences in the antigens and the serodiagnostic technics used in this survey, absolute correlation of test results could not be expected. Nevertheless, the three procedures (IFA, CF, and SF) showed excellent correlation in proven cases of schistosomiasis.