An unknown hydrolase activity of human serum albumin: beta-lactamase activity.

The interaction of a chromogenic cephalosporin, 3-(2, 4 dinitrostyryl)-(6 R, 7 R) -7(2 thienylacetamido)-ceph 3-em-5-carboxylic acid) (nitrocefin) with human serum albumin was studied. Purified human albumin was showed to have a hydrolase activity, catalyzing the decomposition of the chromogenic cephalosporin. The dimeric and trimeric form of albumin also showed this hydrolase activity. The presence of the following amino acid residues at the catalytic site of albumin was demonstrated: tyrosyls 199 and 411, tryptophan 214, lysyls 195, 225 and 240, histidyl 146, also some argynyls were involucrated.