1.Mutation of Arg-166 of alkaline phosphatase alters the thio effect but not the transition state for phosphoryl transfer. Implications for the interpretation of thio effects in reactions of phosphatases.
Holtz KM1, Catrina IE, Hengge AC, Kantrowitz ER. Biochemistry. 2000 Aug 8;39(31):9451-8.
It has been suggested that the mechanism of alkaline phosphatase (AP) is associative, or triester-like, because phosphorothioate monoesters are hydrolyzed by AP approximately 10(2)-fold slower than phosphate monoesters. This "thio effect" is similar to that observed for the nonenzymatic hydrolysis of phosphate triesters, and is the inverse of that observed for the nonenzymatic hydrolysis of phosphate monoesters. The latter reactions proceed by loose, dissociative transition states, in contrast to reactions of triesters, which have tight, associative transition states. Wild-type alkaline phosphatase catalyzes the hydrolysis of p-nitrophenyl phosphate approximately 70 times faster than p-nitrophenyl phosphorothioate. In contrast, the R166A mutant alkaline phosphatase enzyme, in which the active site arginine at position 166 is replaced with an alanine, hydrolyzes p-nitrophenyl phosphate only about 3 times faster than p-nitrophenyl phosphorothioate.
2.Methotrexate analogues. 26. Inhibition of dihydrofolate reductase and folylpolyglutamate synthetase activity and in vitro tumor cell growth by methotrexate and aminopterin analogues containing a basic amino acid side chain.
Rosowsky A, Freisheim JH, Moran RG, Solan VC, Bader H, Wright JE, Radike-Smith M. J Med Chem. 1986 May;29(5):655-60.
Analogues of the antitumor antifolate methotrexate (MTX) were synthesized in which the glutamate (Glu) moiety was replaced by ornithine (Orn), 2,4-diaminobutyric acid (Dab), or 2,3-diaminopropionic acid (Dap). An aminopterin (AMT) analogue with Orn in place of Glu was also synthesized. The MTX analogues were obtained by reaction of 4-amino-4-deoxy-N10-methylpteroic acid (mAPA) and N omega-Boc-alpha,omega-diaminoalkanoic acids in the presence of diethyl phosphorocyanidate, followed by deprotection with trifluoroacetic acid (TFA) or by reaction of p-nitrophenyl-mAPA and N omega-Boc-alpha,omega-diaminoalkanoic acids and subsequent treatment with TFA. The AMT analogue (APA-Orn) was synthesized by reaction of p-nitrophenyl 4-amino-4-deoxy-N10-formylpteroate with silylated N delta-Boc-L-ornithine in DMF at 55 degrees C for 3 days (45% yield), saponification (83%), and TFA cleavage (89%). APA-Orn was a potent inhibitor of both dihydrofolate reductase (DHFR) from L1210 mouse leukemia (IC50 = 0.
3.Release of alkaline phosphodiesterase I from rat kidney plasma membrane produced by the phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis.
Nakabayashi T, Ikezawa H. Cell Struct Funct. 1984 Sep;9(3):247-63.
The release of plasma-membrane-bound enzymes by phosphatidylinositol-specific phospholipase C obtained from Bacillus thuringiensis was investigated. Among the ectoenzymes of plasma membrane tested, alkaline phosphodiesterase I was released markedly from rat kidney cortex slices, in addition to alkaline phosphatase and 5'-nucleotidase. Other membrane-bound enzymes; alanine aminopeptidase, leucine aminopeptidase, dipeptidyl peptidase, leucine aminopeptidase, dipeptidyl peptidase IV, esterase and gamma-glutamyl transpeptidase could not be liberated from the treated slices. Alkaline phosphodiesterase I was released linearly from rat kidney slices with the concentration of phosphatidylinositol-specific phospholipase C, but little enzyme was released from rat liver slices. Alkaline phosphodiesterase I separated from kidney tissue with n-butanol still retained phosphatidylinositol and was transformed into a lower molecular weight form by phosphatidylinositol-specific phospholipase C.
4.Structure and mechanism of PhnP, a phosphodiesterase of the carbon-phosphorus lyase pathway.
He SM1, Wathier M, Podzelinska K, Wong M, McSorley FR, Asfaw A, Hove-Jensen B, Jia Z, Zechel DL. Biochemistry. 2011 Oct 11;50(40):8603-15. doi: 10.1021/bi2005398. Epub 2011 Sep 15.
PhnP is a phosphodiesterase that plays an important role within the bacterial carbon-phosphorus lyase (CP-lyase) pathway by recycling a "dead-end" intermediate, 5-phospho-α-d-ribosyl 1,2-cyclic phosphate, that is formed during organophosphonate catabolism. As a member of the metallo-β-lactamase superfamily, PhnP is most homologous in sequence and structure to tRNase Z phosphodiesterases. X-ray structural analysis of PhnP complexed with orthovanadate to 1.5 Å resolution revealed this inhibitor bound in a tetrahedral geometry by the two catalytic manganese ions and the putative general acid residue H200. Guided by this structure, we probed the contributions of first- and second-sphere active site residues to catalysis and metal ion binding by site-directed mutagenesis, kinetic analysis, and ICP-MS. Alteration of H200 to alanine resulted in a 6-33-fold decrease in k(cat)/K(M) with substituted methyl phenylphosphate diesters with leaving group pK(a) values ranging from 4 to 8.
