title: A model for the regulation of the activity of L-asparaginase/ kinase enzyme of Tetrahymena pyriformis.
abstract: L-Asparaginase of Tetrahymena pyriformis is a lipoprotein with relative M(r) approximately 200 kDa and one subunit size of 39 kDa. This enzyme also exhibits protein kinase activity and it is autophosphorylated in tyrosine residues. Phosphorylation-dephosphorylation of L-asparaginase resulted in complete loss or activation by more than 10-fold of its catalytic activity. Both native and dephosphorylated forms of L-asparaginase are inactivated by phospholipase C and this inactivation can be reversed by the addition of lipids. Based on these results a working hypothesis is suggested that L-asparaginase of T. pyriformis exists in four interconvertible forms: Form A, phosphorylated complexed with lipids, form HA, dephosphorylated (highly active), form I, free of lipids, (inactive) and form B, free of lipids and phosphate.
authors.affiliation: Laboratory of Biochemistry, Aristotelian University of Thessaloniki, Greece.
authors.forename: S A
authors.initials: SA
authors.lastname: Tsirka
authors.forename: D A
authors.initials: DA
authors.lastname: Kyriakidis
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001215:Asparaginase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D008055:Lipids / Q000494:pharmacology; D008954:Models, Biological; D008970:Molecular Weight; D010766:Phosphorylation; D013769:Tetrahymena pyriformis / Q000201:enzymology*; D010738:Type C Phospholipases / Q000494:pharmacology
chemical_list: D008055:Lipids; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D001215:Asparaginase