Protozoa regulation

NOS (eNOS, NOS IH, NOS3). Classically, nNOS and eNOS were considered constitutive enzymes, whereas iNOS is cytokine-induced. Recent evidence suggests that nNOS and eNOS are also subject to important regulation of expression [1 ]. Within the human species, amino acid sequences of the three NOS isoforms share 52-58% identity. Each isoform is well conserved across mammalian species (>90% amino acid identity for nNOS and eNOS, >80% for iNOS). NOS enzymes exist in organisms as low as nematodes, protozoa, and even in plants (Fig. 1). 

Al-Khodor, S., Kalachikov, S., Morozova, I., Price, C., Abu Kwaik, Y. The PmrA/PmrB two-component system of Legionella pneumophila is a global regulator required for intracellular replication within macrophages and protozoa. Infect Immun 77 (2009) 374-386. 

They are especially abundant in many parasitic protozoa and may carry additional glycosyl groupsT Regulation of phospholipid synthesis, which has been studied in detail in yeast, is complex but highly coordinated. The committed step in the synthesis of PE and PC is the hydrolysis of phosphatidafe (PA) by a phosphafase to generate diacylglycerols (Fig. 

With respect to amino acid metabolism some of the differences between host and parasite are somewhat subtle. Some parasite enzymes, for example, have properties which are clearly distinct from those of their mammalian counterparts, such as the cofactor dependence and regulation of glutamate dehydrogenases. The utilization of specific amino acids such as proline or the accumulation of others such as alanine reflects a difference in the relative importance of the pathways between parasite and host. Some differences are particularly striking, especially among anaerobic protozoa in... 

A cell wall, when present, provides external support but does not regulate permeability which is the function of the plasma membrane, a totally different structure (see next Section). A total lack of cell walls is one of the outstanding features of the animal kingdom. Only in a small proportion of unicellular animals can cell walls be found, as in Eimeria and Chlamydomonas which have walls of protein and cellulose, respectively. Yet the majority of the protozoa, including Amoeba and Trypanosoma, lack this outer cage. Cell walls are, however, a special feature of plants (including fungi) and bacteria. 

I have talked mostly about eukaryotic cells, so I should mention here the regulation of RNA polymerase of E. coli by an ADPRT of phage T4. This example, and the presence of ADPRT enzymes in protozoa such di Physarum polycephaluniy Tetrahymena pyriformis, Dictyosteleum discoideum, Trypanosoma cruzi, Trypanosoma brucei and probably va Plasmodium spp. show that ADPRT enzymes evolved at a fairly early stage in evolution. 

Very abundant lipid in animals, plants, and microorganisms Trace lipid in animals, plants, and microorganisms Present in animals, plants, and microorganisms Common in animals, plants, and microorganisms regulator of vital cell processes Found mainly in protozoa and marine invertebrates... 

HABTE M. and ALEXANDER M. 1977. Further Evidence for the Regulation of Bacterial Populations in Soil by Protozoa. Archives of Microbiology, 113, 181-183. 

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