Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.64 (proteinase K)
 4,071 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reaction of protein amino groups with glucose leads to the formation of a stable Amadori product via a Schiff base adduct, which is further converted to advanced glycosylation end products (AGE) with color and unique fluorescence characteristics. 2-(2-Furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI) was recently identified as a major fluorescent compound (Ponger, S., Ulrich, P.C., Bencsath, F.A., and Cerami, A. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 2684-2688). Its in vivo and in situ presence was further demonstrated by radioimmunoassays (Chang, J.C.F., Ulrich, P.C., Bucala, R., and Cerami, A. (1985) J. Biol. Chem. 260, 7970-7974). In the present study the occurrence of FFI in AGE-proteins was reassessed. The radioimmunoassay using anti-FFI antibody and high performance liquid chromatography failed to detect FFI in AGE samples obtained from bovine serum albumin, poly-L-lysine, oligo-L-lysine, and L-lysine. Even after acid hydrolysis or proteinase K digestion, FFI was undetectable. To our surprise, however, the addition of ammonia to these acid hydrolysate led to the production of FFI, suggesting the importance of acid hydrolysis and subsequent reaction with ammonia for the generation of FFI. This observation was fully supported by model experiments using AGE-samples prepared by incubating glucose with monoaminocarboxylic acids such as beta-alanine, gamma-aminobutyric acid, and epsilon-aminocaproic acid. Thus, a nonfluorescent FFI precursor is produced by acid hydrolysis, and its conversion to fluorescent FFI occurs upon subsequent reaction with ammonia, the evidence against the presence of FFI in AGE-proteins.
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PMID:Evidence against in vivo presence of 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole, a major fluorescent advanced end product generated by nonenzymatic glycosylation. 319 1

Protein amino groups can react with glucose without the aid of enzymes to form stable Amadori products containing 1-amino-1-deoxyketose residues. These adducts can undergo subsequent rearrangements and dehydrations to form various brown and fluorescent pigments. Recently, a chromophore, 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI), was isolated from acid hydrolysates of bovine serum albumin (BSA) and poly-L-lysine which had been incubated with glucose. To confirm the presence of FFI in situ, a radioimmunoassay was developed. A derivative of FFI, 4-furanyl-2-furoyl-1H-imidazole-1-hexanoic acid, was coupled to BSA and used to immunize rabbits. A radioactive FFI derivative was synthesized by reaction of 2-furyl-glyoxal with gamma-amino-[2,3-3H]butyric acid to form FFI-[3H]butyric acid. The resultant antiserum showed binding affinity to FFI and cross-reactivity for related compounds. FFI bound to proteins was liberated by acid hydrolysis or digestion by proteinase K prior to measurement. A linear relationship was seen between the amount of FFI equivalent detected and the amount of acid hydrolysate or enzymatic digest assayed. Poly-L-lysine and BSA incubated with glucose showed a time-dependent increase in the amounts of fluorescence and FFI equivalence. The detection of a time-related increase in the amount of FFI or a closely related structure in enzymatically digested proteins implicates it as an in situ product on proteins which have undergone the Maillard reaction with glucose. Of physiological significance is that FFI could also be detected in human globin and serum albumin from normal individuals. Thus, proteins exposed to glucose in vitro and in vivo form FFI as an in situ glycosylation product.
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PMID:Detection of an advanced glycosylation product bound to protein in situ. 400 86