No abstract

No abstract

A new enzyme, fructosyl-amino acid oxidase (fructosyl-a-L-amino acid: oxygen oxidoreductase (defruetosviating)) was found, which decomposes Amadori rearrangement compounds of a-i-amino acids to the corresponding a-ketoaldehydes and a-L-amino acids. The enzymewas purified from a strain of Corynebacterium sp. about 38.9-fold to a single protein band with an overall yield of 35 % from the crude extract, and crystallized in rhombic plates. The molecular weight of the enzymewas about 88,000 on gel filtration and 44,000 on SDS-polyacrylamide gel electrophoresis. Non-covalently bound FADwas the prosthetic group. Its isoelectric point was pH 4.6. The optimum pH of the enzyme reaction in potassium phosphate buffer was about 8.3. Fructosyl-a-L-amino acid was the substrate having the highest susceptibility to the enzyme, but /V-fructosyl derivatives of other materials, such as /J-amino acids, L-imino acids, D-amino acids, alkyl amines, and ammonia, showed almost no susceptibility. The apparent Kmvalues for fructosyl-glycine and fructosyl-phenylalanine were 0.74 mM and 0.71 mM, respectively. The enzyme was inhibited by Hg2+ and Pb2+. The Maillard reaction had been studied for a long time as an aspect offood chemistry.1~3) Recently, it came to be known that the reaction proceeds non-enzymatically even in living bodies. Accordingly, it is regarded from the biochemical viewpoint. Amadori rearrangement products are formed at an early stage of the Maillard reaction by appending a reducing sugar to the amino residue of proteins or nucleic acids.4'5

No abstract

No abstract