Evidence of human serum albumin beta-lactamase activity.

The beta lactamase activity of serum albumin was measured using a chromogenic cephalosporin: 3-(2,4 dinitrostyryl) -(6 R, 7R) - 7 -(2 thienacetamido) ceph 3 - em 4 carboxylic acid) (nitrocefin). It was found that albumin of different species and purity, obtained from a variety of sources, showed a significant beta lactamase activity. The reaction presented a saturation kinetics, with a KM of 1.42 10(-5) M. Oleic acid and ibuprofen inhibited the reaction, suggesting that the cephalosporin and these ligands are bound to the same site in albumin. The tertiary structure of albumin is necessary for the catalytic activity to be present probably unprotoned lysine residues in the catalytic site of albumin are related with this activity.