240
PHOSPHATASES IN EIMERIA TENELLA
[ Vol. XXIV, Part IV,
acids and phosphoric acid and (2) dehydration of metaphosphoric acid [Roche,
1951]. They may be specific for one bond, e.g. phosphomonoesterases, phospho-
diesterases, pyrophosphatases, etc., or specific for one or several substrates, e.g.
adenosine-triphosphatase, 5-nucleotidase, etc.
There are four phosphomonoesterases, i.e. those enzymes which catalyse
orthophosphoric monoesters [Folley and Kay, 1936 ; Roche and Curtois, 1943 ;
Roche, 1942] : the first two of the series, phosphomonoesterase I and II are commonly
known as alkaline and acid phosphatase respectively as they exhibit optimum
stability at pH 9.3-9.8 ; and 4.5-5.5 in the order written [Roche, 1951]. They
are found in a wide variety of mammalian organs. Alkaline phosphomonoesterase
activity is specially intense (1) in intestine (brush border, and Golgi region) where it
catalyses phosphorylation and synthesis of neutral fat [Jeker, 1936 ; Dempsey and
Wislocki, 1946], (2) in ossifying bone [first shown by Robison, 1923] where it hy-
drolyses blood esters glucose and 1-phosphate with the liberation of PO 4 ions which
precipitate Ca ++ to lay down bone Ca 3 (Po 4 ) 2 [Roche, 1947], and (3) in kidney
[in mitochondria ; Dounce, 1951] where it is perhaps concerned with the reabsorption
of glucose from the lumen of tubules [Moog, 1946 ; March and Drabkin, 1947].
5-Nucleotidase specifically hydrolyses 5-nucleotides (adenosine-5-phosphate
and inosine-5-phosphate) but not the 3-nucleotides (adenosine-triphosphate and
yeast nucleic acid).
The participation of phosphatases in cell metabolism has not been precisely
understood. The universality of their distribution suggests that they may have
a general role to play in all processes. The metabolic importance of energy yielding
phosphate bond is developed through an independent system of phosphorylating
enzymes. Phosphatase synthesis of esters seems to have little physiological im-
portance. Only the specific phosphatase, e.g. 5-nucleotidae takes part in this
metabolism as far as the hydrolysing activity in liberating phosphates are concerned
[Roche, 1951]. Definitely, they are known to catalyse transphosphorylation
processes. Danielli [1953] attaches considerable importance to this role of alkaline
phosphatase. He suggests that 'alkaline phosphatase may act as a phosphokinase
in the conservation of phosphate bond energy. If gene products must be dephosph-
orylated to release products of gene in an active form a considerable economy of the
energy of phosphate bond would be affected if instead of hydrolysing the phosphate
bond, the phosphate were transferred to some other molecule : alkaline phosphatase
would act as catalyst for such transfers '. Alternately he believes that nucleus
may normally be synthesising phosphate bonds, and that the function of alkaline
phosphatase is to transfer phosphate groups from precursor substances to the specific
molecules which are involved in the activity of the genes.
Relation between phosphatases and nucleic acids of Eimeria tenella
Perhaps the most significant and interesting fact emerging from the present study
is the demonstration of the constant presence of phosphatases in the nucleus of the
parasite. Its enzymic activity is particularly very high in the karyosomes through-
out the endogenous phase of E. tenella whereas it is of moderate intensity in the
nucleoplasm. Karyosome of protozoa is comparable to the nucleolus of a mammalian
cell. These observations are of considerable interest, since in view of the work of