Escherichia coli inorganic pyrophosphatase : site-directed mutagenesis of the metal binding sites

AbstractAspartic acids 65, 67, 70, 97 and 102 in the inorganic pyrophosphatase of Escherichia coli, identified as evolutionarily conserved residues of the active site, have been replaced by asparagine. Each mutation was found to decrease the κapp value by approx. 2–3 orders of magnitude. At the same time, the Km values changed only slightly. Only minor changes take place in the pK values of the residues essential for both substrate binding and catalysis. All mutant variants have practically the same affinity to Mg2+ as the wild-type pyrophosphatase

Mg2+ activation of Escherichia coli inorganic pyrophosphatase

AbstractFurther refinement of X-ray data on Escherichia coli inorganic pyrophosphatase [Oganessyan et al. (1994) FEBS Lett. 348, 301–304] to 2.2 Å reveals a system of noncovalent interactions involving Tyr55 and Tyr141 in the active site. The pKa for one of the eight Tyr residues in wild-type pyrophosphatase is as low as 9.1 and further decreases to 8.1 upon Mg2+ binding, generating characteristic changes in the absorption spectrum. These effects are lost in a Y55F but not in a Y141F variant. It is suggested that the lower-affinity site for Mg2+ in the enzyme is formed by Tyr55 and Asp70, which are in close proximity in the apo-enzyme structure

Физико-химические основы химии и технологии платиновых металлов и их соединений

The date of investigation on chemistry and technology of platinum metals in the large years are presented. The complexes of palladium(II) with macroheterocyclyc compounds are syntesited. The application of electrochemical processes for selection of platinum metals from solutions and applyed of concentrate of platinum metals is shownКратко рассмотрены результаты выполненных в последние годы работ в области химии и технологии платиновых металлов. Выполнен синтез комплексов палладия(II) с макрогетероциклическими соедине-ниями. Показана возможность применения электрохимического метода для извлечения платиновых металлов из растворов и получения концентратов