The effect of pH and temperature on structure, stability, activity and
enantioselectivity of haloalkane dehalogenase DbjA from Bradyrhizobium
japonicum USDA110 was investigated in this study. Conformational
changes have been assessed by circular dichroism spectroscopy, functional
changes by kinetic analysis, while quaternary structure was studied by gel
An amidase acting on (R,S)-piperazine-2-tert-butylcarbox-amide was purified fromPseudomonas azotoformansIAM
1603 and characterized. The enzyme actedS-stereoselec-tively on (R,S)-piperazine-2-tert-butylcarboxamide to yield
(S)-piperazine-2-carboxylic acid. N-terminal and internal
amino acid sequences of the enzyme were determined.
ThegeneencodingtheS-stereoselective piperazine-2-tert-butylcarboxamide amidase was cloned from the chromo-somal DNAof the strain and sequenced.
A novel amidase acting on (R,S)-piperazine-2-tert-butyl-carboxamide was purified fromPseudomonassp. MCI3434
and characterized. The enzyme acted R-stereoselectively
on (R,S)-piperazine-2-tert-butylcarboxamide to yield (R)-piperazine-2-carboxylic acid, and was tentatively named
R-amidase. The N-terminal amino acid sequence of the
enzyme showed high sequence identity with that deduced
from a gene named PA3598 encoding a hypothetical
hydrolase in Pseudomonas aeruginosaPAO1.
Review material published this year includes an essay ‘the unexpected and the
unpredictable in organic synthesis’ which is a valuable account by Mukaiyama
of the extraordinary history of his research, sections on stereoselective routes
to sugars and glycosides being of special relevance.’
Although the technologies on chiral/enantiomer separation and stereoselective analysis
have matured in the past ca. 20 years, the development of new, even more advanced
chiral separation materials, mechanisms and methods still belong to the more challenging
tasks in separation science and analytical chemistry. An analysis of recent
trends indicates that capillary electrophoresis (CE) can show real advantages over
chromatographic methods in ultratrace chiral determination of biologically active ionogenic
compounds in complex matrices, including mostly biological ones....
We addressed the ability of various organophosphorus (OP) hydrolases to
catalytically scavenge toxic OP nerve agents. Mammalian paraoxonase
(PON1) was found to be more active than Pseudomonas diminutaOP
hydrolase (OPH) and squidO,O-di-isopropyl fluorophosphatase (DFPase)
in detoxifying cyclosarin (O-cyclohexyl methylphosphonofluoridate) and
soman (O-pinacolyl methylphosphonofluoridate).
Kinetic experiments with a substrate series of phenylacetyl-arylamides reveal that at least one polar group in the amine
moiety is required for the proper orientation of the substrate
in the large nucleophile-binding subsite of penicillin acylase
ofEscherichia coli. Quantum mechanical molecular model-ling of enzyme–substrate interactions in the enzyme active
site shows that in the case of substrates lacking local sym-metry, the productive binding implies two nonsymmetrical
arrangements with respect to the two positively charged
guanidinium residues of ArgA145 and ArgB263....
-dependent (R)-2-hydroxyglutarate dehydrogenase (HGDH) cata-lyses the reduction of 2-oxoglutarate to (R)-2-hydroxyglutarate and belongs
to the D-2-hydroxyacid NAD
-dependent dehydrogenase (D-2-hydroxyacid
dehydrogenase) protein family. Its crystal structure was determined by
phase combination to 1.98 A˚
resolution. Structure–function relationships
obtained by the comparison of HGDH with other members of theD-2-hydroxyacid dehydrogenase family give a chemically satisfying view of the
substrate stereoselectivity and catalytic requirements for the hydride trans-fer reaction.
We have determined the nucleotide sequence of a DNA fragment covering
the flanking region of the R-stereoselective amidase gene, ramA, from the
Pseudomonassp. MCI3434 genome and found an additional gene, bapA,
coding for a protein showing sequence similarity to DmpA aminopeptidase
from Ochrobactrum anthropiLMG7991 (43% identity).