Tohru Takarada

Metal-ion-assisted hydrolysis of dipeptides involving a serine residue in a neutral aqueous solution

Dipeptides having a serine residue at the C-terminus, X-Ser, where X is an appropriate amino acid residue, were efficiently hydrolyzed in the presence of ZnCl2 at pH 7.0. The rapid hydrolysis of X-Ser is due to an autocatalysis of the hydroxy group in the serine residue, and is found to be accelerated by a metal ion, in particular by ZnCl2. Roles of the metal ion in the hydrolysis of peptides involving a serine residue, in relation to the recently reported protein cleavages, are discussed.

Solubilization of lanthanide ions by cyclodextrins in basic aqueous solutions

Cyclodextrins form complexes with lanthanide ions in basic aqueous solutions. This complex formation in basic solution dramatically enhances the solubility of lanthanide ions, which are otherwise insoluble due to the formation of hydroxide gels. Solutions of the γ-cyclodextrin-Ce3+ complex effectively hydrolyze 2′-deoxyadenosine-5′-monophosphate to 2′-deoxyadenosine.

Lanthanide ion-induced hydrolyses of alkyl esters and amides of α-amino acids†

Lanthanide ion-induced hydrolyses of methyl esters, ethyl esters, and amides of α-amino acids were systematically studied. In the hydrolysis of the alkyl esters, all the lanthanide ions are effective and the catalytic activities decrease in the order Ce(III), Nd(III)u2005>u2005Sm(III)u2005>u2005Eu(III)u2005>u2005Gd(III), Ce(IV)u2005>u2005Pr(III)u2005>u2005Dy(III), Tb(III), Er(III), Ho(III), Tm(III)u2005>u2005La(III), Lu(III), Yb(III). For the hydrolysis of the amides, however, the Ce(IV) ion is overwhelmingly more active than other lanthanide(III) and non-lanthanide ions. The results are interpreted in terms of the difference in the rate-limiting step for these two reactions.