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Xylose isomerase (E.C.5.3.1.5) catalyzes the interconversion of aldose and ketose sugars and has an absolute requirement for two divalent cations at its active site to drive the hydride transfer rates of sugar isomerization. Atomic resolution data not only provide structural clues to atomic motions but also can be used for descriptive computational approaches.

Structural and biochemical evidence suggest that the 3-keto-L-gulonate 6- phosphate decarboxylase (KGPDC) reaction proceeds via a Mg(super 2+)-stabilized 1,2-cis-enediolate intermediate. The catalytic roles of conserved residues in the active site of KGPDC is defined and demonstrated that even though KGPDC and orotidine 5'-monophosphate decarboxylase (OMPDC) share a common active site architecture, each enzyme uses this architecture to catalyze reactions with unrelated substrate specificity and unrelated reactions mechanisms.

The study highlights the opportunistic nature of divergent evolution in conscripting the active site of a progenitor to catalyze a mechanistically distinct reaction. In the report about the structure of the Mg(super 2+)-requiring 3-keto-L-gulonate 6-phosphate decarboxylase (KGPDC), a mechanism is suggested in which the 2-OH group and 3-keto group, the substrate are liganded to the Mg(super 2+).

The role of adenosine 5-triphosphate (ATP) in the activation mechanism of alpha-ca(super 2+)/calmodulin-dependent protein kinase II(alpha CaMKII) was investigated using the T286A non-autophosphorytable mutant of alphaCaMKII. Electron micrographic images of negatively stained T286A-alphaCaMKII mutant protein had a similar appearance to those of dodecameric alphaCaMKII.

Structures of the R-state of Escherichia coli ATCase maintained with carbamyl phosphate and succinate, phosphonoacetamide and malonate, or phosphonacetyl-L-aspartate (PALA) have previously made in the space group P321, in which the two independent r (regulatory) and two independent c (catalytic) chains are repeated. In the p2(sub 1)2(sub 1)2(sub 1) space group there are no crystallographic constraints other than the crystal packing.

The structure of Escherichia coli ligated of products (phosphate and N-carbamy-L-aspartate) is determined at 2.37-angstrom resolution. The new structure shows that no residues block the probable leaving pathway for carbamylaspartate (CLA). The process suggested there allows CLA to leave the enzyme before phosphate leaves from its new site.

Significantly altering the amphipathic structure of a lytic peptide by reshuffling its sequence and/oreplacing a few L-amino acids with their D-enantinomers did not significantly affect the antimicrobial activity of the peptides nor their ability to bind and permeate negatively charged (PE/PG) membranes. This study clearly enables differentiating between the modes of action of an amphipathic alpha-helical lytic peptide, its sequence altered analogues, and their diastereomers.

Lipoyl synthase catalyzes the formation of the lipoyl cofactor, which is employed by several multienzyme complexes for the oxydative decarboxylation of various alpha-keto acids generating N(super 5),N(super 10)-methylenetetrahydrofolate. Their results indicate that 24% of the 5-dA does not lead to [lipoyl]H-protein (LHP) formation during the time span of the assay.

Genetic studies indicate that Escherichia coli possesses three enzymes capable of phosphorylating glucose efficiently. Findings suggest that modern genomes harbor a wealth of latent enzyme activities and that extant metabolic pathways are equivocal.

Cytidine tirphosphate synthetases (CTPSs) produce CTP from UTP and glutamine, and regulateintracellular CTP levels through interactions with four ribonucleotide triphosphates. The tetramer is generated from the noncrystallographic AB dimer by the 2-fold crystallographic rotation about the c axis.