Enzyme-Substrate Intermediate Formation at Lysine 329 of Human Deoxyhypusine Synthase

Homospermidine synthase, the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis, evolved from deoxyhypusine synthase.

Pyrrolizidine alkaloids are preformed plant defense compounds with sporadic phylogenetic distribution. They are thought to have evolved in response to the selective pressure of herbivory. The first pathway-specific intermediate of these alkaloids is the rare polyamine homospermidine, which is synthesized by homospermidine synthase (HSS). The HSS gene from Senecio vernalis was cloned and shown t...

Molecular cloning and functional expression of human deoxyhypusine synthase cDNA based on expressed sequence tag information.

Deoxyhypusine synthase is an NAD(+)-dependent enzyme that catalyses the formation of a deoxyhypusine residue on the eukaryotic initiation factor 5A (eIF-5A) precursor by transferring an aminobutyl moiety from spermidine to the epsilon-amino group of a unique lysine residue. We have recently cloned and characterized the Neurospora crassa deoxyhypusine synthase cDNA using a reverse genetics appro...

Purification and properties of uroporphyrinogen I synthase from human erythrocytes. Identification of stable enzyme-substrate intermediates.

The ferrous-dioxygen intermediate in human cytochrome P450 3A4. Substrate dependence of formation and decay kinetics.

The oxy-ferrous complex is the first of three branching intermediates in the catalytic cycle of cytochrome P450, in which the total efficiency of substrate turnover is curtailed by the side reaction of autoxidation. For human membrane-bound cytochromes P450, the oxy complex is believed to be the primary source of cytotoxic superoxide and peroxide, although information on the properties and stab...

Evidence for a Catalytically and Kinetically Competent Enzyme–Substrate Cross-Linked Intermediate in Catalysis by Lipoyl Synthase

Lipoyl synthase (LS) catalyzes the final step in lipoyl cofactor biosynthesis: the insertion of two sulfur atoms at C6 and C8 of an (N(6)-octanoyl)-lysyl residue on a lipoyl carrier protein (LCP). LS is a member of the radical SAM superfamily, enzymes that use a [4Fe-4S] cluster to effect the reductive cleavage of S-adenosyl-l-methionine (SAM) to l-methionine and a 5'-deoxyadenosyl 5'-radical (...