L-Lysine-α-Ketoglutarate ε-Aminotransferase
Properties of the Bound Pyridoxal 5'-Phosphate
1977 Volume 82 Issue 2 Pages 535-543
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1977 Volume 82 Issue 2 Pages 535-543
L-Lysine-α-ketoglutarate ε-aminotransferase of Flavobacterium lutescens (Achromobacter liquidum) IFO 3084 shows positive circular dichroic bands at 340 and 415nm where absorption maxima are observed, and fluorescence maxima at 380 and 490nm on excitation at 340 and 415nm, respectively. The pyridoxal 5'-phosphate absorbing at 415nm is bound through an aldimine linkage to an ε-amino group of the lysine residue of the protein. Upon aging, the 415nm pyridoxal 5'-phosphate changes to a less active form (λmax, 325nm), which is distinguishable from the 340nm pyridoxal 5'-phosphate. This 325nm bound pyridoxal 5'-phosphate is reduced with sodium borohydride and shows no circular dichroism. When the semiapoenzyme is aged under the same conditions, no spectral change is observed. These findings suggest that the pyridoxal 5'-phosphate bound through an aldimine linkage may be converted into a carbinol amine or some other related form by aging.
