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Biomedical subjects

A Lucacchini

Publications and source records attributed to A Lucacchini.

10 recordsLinked to original sources
PubMed1979

Affinity labeling of histidine and lysine residue in the adenosine deaminase substrate binding site.

1. Adenosine deaminase was inactivated by 9-(4-bromoacetamidobenzyl)-adenine (I) and 9-(2-bromoacetamidobenzyl)adenine (II), two affinity labels. 2. The stoichiometry of the reaction with reagent II is reported: 1 mol reagent is bound per mol inactive enzyme. Amino acid analysis of the 6 N HCl hydrolyzate of the inactive enzyme identified CM-histidine as the main alkylation product. This is the first evidence of the presence of a histidine in the active site region. 3. The alkylation rate and involved amino acid residues were studied for both reagents I and II, at pH 8 and 5.5. The particular reactivity of a lysine near or in the active site is discussed.

Adenine↗
PubMed1975

A general method of purification of adenosine deaminase by affinity chromatography.

Affinity chromatography has been used to purify adenosine deaminase from various sources: calf spleen, calf intestinal mucosa, chicken duodena and human erythrocytes. For this purpose a specific inhibitor, 9-(p-aminobenzyl) adenine, was synthesized and covalently joined to agarose. Adenosine deaminase is selectively retained by such an inhibitor-resin when highly impure solutions are chromatographed through it. After elution from the resin with guanylurea, a competitive inhibitor, the enzyme is homogeneous and can be recovered in yields of 80 percent or more and the same number of multiple forms of the enzyme is present in the purified preparation and in the crude extract.

Adenine↗
PubMed1975

Digestion of insulin derivatives with subtilisin: a kinetic study.

Native, denatured, performic acid-oxidized or S-sulfo insulin and S-sulfo or performic acid-oxidized A- and B-chains were digested with subtilisin type Carsberg. The proteolysis was followed by measuring the uptake of alkali through autotitration. The kinetic study shows the existence of 2 first-order reaction classes which differ markedly in rate constant. The number of bonds split with fast and with slow reactions has been calculated. Only one of a total of 12 cleavable bonds in native insulin is opened by fast reaction. In the denatured protein the number of bonds split by the fast reaction increases to 4 and in the oxidized and S-sulfo protein 3 bonds are cleaved, while the slow cleavable bonds number 2 and 7, respectively, The kinetic study of the proteolysis of S-sulfo A-chain and of oxidized or S-sulfo B-chain shows that two bonds are split in A-chain with the fast and slow reactions, while in B-chain only one of the six cleavable bonds is susceptible to fast attack.

Hydrogen Bonding↗
PubMedDate not supplied

A powerful inhibitor of guanine deaminase.

The synthesis of 9-(p-carbetoxyphenyl) guanine is reported. The assays carried out on guanine deaminase from rat and rabbit liver and pig brain show that this compound is a powerful inhibitor. The compound has a Ki = 5 micronM for the enzyme from pig brain. The use of the inhibitor for the synthesis of a specific adsorbent for guanine deaminase was studied.

Aminohydrolases↗