Metal ion and vitamin B₆ catalyzed oxidative deamination of some amino acids in the presence of molecular oxygen /
| Main Author: | |
|---|---|
| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
|
| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Protonation constants of vitamin B₆ coenzymes; pyridoxal-5'- phosphate(PLP), 5'-deoxypyridoxal(DPL), and synthetic amino acids; α-phenylglycine, 4-methoxyphenylglycine and 4-sulfophenylglycine are determined potentiometrically at 25°C and at an ionic strength of 0.10 M (KNO₃). Stability constants for the complexes of Mn (II), Co (II), Ni (II), Cu (II) and Zn (II) with these ligands were evaluated. Potentiometric investigation of Schiff base reaction between pyridoxal derivatives and amino acids indicates that the extent of conversion gradually increases with pH until a maximum is reached around pH 8.5. A substantial increase in the extent of Schiff base reaction was observed in the presence of metal ions. The equilibrium formation of 1:1 and 2:1 Schiff base:metal chelates in ternary systems containing pyridoxal derivatives, amino acids and metal ions was investigated. Stabilities of 1:1 Cu (II)-Schiff base chelates were the greatest among those studied. The formation of hydroxo complexes of Cu (II)-Schiff base chelates in basic solutions, was observed. The oxidative deamination of p-sulfophenylglycine by pyridoxal 5'-phosphate and 5'-deoxypyridoxal was studied in detail. The reaction proceeds at an appreciable rate in alkaline solutions in the presence of Cu (II) ion and molecular oxygen. The reaction yielded the keto acid, p-sulfophenylglyoxylic acid and ammonia as products. Spectroscopic studies indicate rapid conversion of the Schiff base to the oxime of pyridoxal derivatives. The oxime slowly released hydroxylamine and the regenerated coenzyme reacted with amino acid to continue the catalytic process. Hydroxylamine formed in the solution rapidly decomposes to ammonia. After the completion of the first cycle, oxidative deamination proceeds at substantially lower rate while the concentration of the oxime intermediate remains approximately constant. The overall conversion of amino acid to keto acid was followed by the isolation and identification of ammonia and keto acid formed by the reaction. Kinetics of the formation of the oxime intermediate were investigated as a function of pH and temperature. Initial rates of reaction in 5'-deoxypyridoxal-Schiff base systems were higher than those in pyridoxal 5'-phosphate-Schiff base systems. The mechanistic aspects of the reaction are analyzed. |
|---|---|
| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemistry." |
| Physical Description: | xiv, 135 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |