2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) is an enzyme highly abundant in the central nervous system myelin of terrestrial vertebrates. The catalytic domain of CNPase belongs to the 2H phosphoesterase superfamily and catalyzes the hydrolysis of nucleoside 2',3'-cyclic monophosphates to nucleoside 2'-monophosphates. The detailed reaction mechanism and the essential catalytic amino ac...

Xylose isomerase (XI) catalyzes the isomerization and epimerization of hexoses, pentoses and tetroses. In order to clarify the reasons for the low reaction efficiency of a pentose sugar, L-arabinose, we determined the crystal structure of Streptomyces rubiginosus XI complexed with L-arabinose. The crystal structure revealed that, when compared with D-xylose and D-glucose, L-arabinose binds to t...

An artificial enzyme was constructed by attaching short peptides with active sites (SHELKLKLKL, WLKLKLKL) onto carbon nanotubes (CNT). It was found that the combination of SHE amino acids was essential to form a catalytic triad. W was also incorporated into this artificial enzyme and acted as a substrate binding site, thus producing an enzyme model with synergism of 67.7% catalytic groups and 3...

The catalytic and regulatory subunits of cAMP-dependent protein kinase (PKA) are highly dynamic signaling proteins. In its dissociated state the catalytic subunit opens and closes as it moves through its catalytic cycle. In this subunit, the core that is shared by all members of the protein kinase family is flanked by N- and C-terminal segments. Each are anchored firmly to the core by well-defi...

ATP synthase uses a unique rotary mechanism to couple ATP synthesis and hydrolysis to transmembrane proton translocation. The F(1) subcomplex has three catalytic nucleotide binding sites, one on each beta subunit, with widely differing affinities for MgATP or MgADP. During rotational catalysis, the sites switch their affinities. The affinity of each site is determined by the position of the cen...

Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of 6-oxy-purine nucleosides to the corresponding purine base and alpha-D-ribose 1-phosphate. Its genetic loss causes a lethal T cell deficiency. The highly reactive ribocation transition state of human PNP is protected from solvent by hydrophobic residues that sequester the catalytic site. The catalytic site was enlarged by repl...

Pokeweed antiviral protein (PAP) is a ribosome-inactivating protein that catalytically cleaves a specific adenine base from the highly conserved alpha-sarcin/ricin loop of the large ribosomal RNA, thereby inhibiting protein synthesis at the elongation step. Recently, we discovered that alanine substitutions of the active center cleft residues significantly impair the depurinating and ribosome i...

Tn5 transposase (Tnp) is a 53.3-kDa protein that is encoded by and facilitates movement of transposon Tn5. Tnp monomers contain a single active site that is responsible for catalyzing a series of four DNA breaking/joining reactions at one transposon end. Based on primary sequence homology and protein structural information, we designed and constructed a series of plasmids that encode for Tnps c...

Heme-copper oxidases catalyze the four-electron reduction of O2 to H2O at a catalytic site that is composed of a heme group, a copper ion (CuB), and a tyrosine residue. Results from earlier experimental studies have shown that the O-O bond is cleaved simultaneously with electron transfer from a low-spin heme (heme a/b), forming a ferryl state (PR ; Fe4+=O2-, CuB2+-OH-). We show that with the Th...

All serotypes of botulinum toxin possess a disulfide bond that links the heavy chain and light chain components of the holotoxin. Experiments were done to assess the functional significance of this covalent bond, and the work was facilitated by use of mercurial compounds that modify residues in the vicinity of the catalytic site. The data indicated that reduction of the interchain disulfide bon...