Molecular Imaging of Hydrolytic Enzymes Using PET and SPECT.

Hydrolytic enzymes are a large class of biological catalysts that play a vital role in a plethora of critical biochemical processes required to maintain human health. However, the expression and/or activity of these important enzymes can change in many different diseases and therefore represent exciting targets for the development of positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radiotracers. This review focuses on recently reported radiolabeled substrates, reversible inhibitors, and irreversible inhibitors investigated as PET and SPECT tracers for imaging hydrolytic enzymes.

Imaging of enzyme replacement therapy using PET.

Direct enzyme replacement therapy (ERT) has been introduced as a means to treat a number of rare, complex genetic conditions associated with lysosomal dysfunction. Gaucher disease was the first for which this therapy was applied and remains the prototypical example. Although ERT using recombinant lysosomal enzymes has been shown to be effective in altering the clinical course of Gaucher disease, Fabry disease, Hurler syndrome, Hunter syndrome, Maroteaux-Lamy syndrome, and Pompe disease, the recalcitrance of certain disease manifestations underscores important unanswered questions related to dosing regimes, tissue half-life of the recombinant enzyme and the ability of intravenously administered enzyme to reach critical sites of known disease pathology.

Directed "in situ" inhibitor elongation as a strategy to structurally characterize the covalent glycosyl-enzyme intermediate of human pancreatic alpha-amylase.

While covalent catalytic intermediates of retaining alpha-transglycosylases have been structurally characterized previously, no such information for a hydrolytic alpha-amylase has been obtained. This study presents a new "in situ" enzymatic elongation methodology that, for the first time, has allowed the isolation and structural characterization of a catalytically competent covalent glycosyl-enzyme intermediate with human pancreatic alpha-amylase. This has been achieved by the use of a 5-fluoro-beta-l-idosyl fluoride "warhead" in conjunction with either alpha-maltotriosyl fluoride or 4'-O-methyl-alpha-maltosyl fluoride as elongation agents.

Covalent inhibitors of glycosidases and their applications in biochemistry and biology.

Glycoside hydrolases are important enzymes in a number of essential biological processes. Irreversible inhibitors of this class of enzyme have attracted interest as probes of both structure and function. In this review we discuss some of the compounds used to covalently modify glycosidases, their use in residue identification, structural and mechanistic investigations, and finally their applications, both in vitro and in vivo, to complex biological systems.

A homology model for human alpha-l-iduronidase: insights into human disease.

Genotype-phenotype correlations in genetic diseases for which missense mutations lead to disease remain a challenge. This is particularly true for diseases caused by alterations of proteins for which no three-dimensional structure is available. One such disease is Mucopolysaccharidosis type I, a disorder arising from a lack of activity of the lysosomal enzyme alpha-l-iduronidase (IDUA, EC 3.

Characterization of the recognition of blood group B trisaccharide derivatives by the lectin from Marasmius oreades using frontal affinity chromatography-mass spectrometry.

A novel lectin from the mushroom Marasmius oreades (MOA) has been shown to bind to human blood group B oligosaccharides [1]. In the present work we examine the binding of a series of analogues of the blood group B-trisaccharide, alphaGal(1-3)[alphaFuc(1-2)]betaGal-OR (1, R = (CH2)8COOMe). MOA was biotinylated and immobilized on a micro column (9.