REACTION OF ALDOSES WITH AMINO-ACIDS AND PROTEINS .2. REACTION OF HUMAN-SERUM ALBUMIN WITH ALDOSES

The reaction of human serum albumin (HSA) with aldoses (C3-C6) and acetaldehyde has been studied. U.v. and fluorescent spectra of the HSA-glyceraldehyde and HSA-GlcN adducts reveal yellow chromophores absorbing at 300-350 nm and emitting at 435 nm. However, even limited reaction of HSA with acetaldehyde induced perturbation in the Trp microenvironment. C.d. spectra of the adducts show an average 20% decrement in mean residual ellipticity [θ], which is independent of the extent of the reaction and the aldose used. It is concluded that most of the reactions with aldoses occur at the surface of the HSA molecule. With the exception of the GlcN adduct, the HSA adducts rearrange to produce pyrrole rings on the protein surface. I.e.f. analysis shows that the pI values of the modified HSA are almost linearly correlated with the chain length of the reacting aldose: from pI 4.2 for HSA-glyceraldehyde up to pI 5.0 for HSA-GlcN.