Beta-lactamase with high molecular weight: evidence for an interaction with neuraminic acid-containing structures

The constitutive beta-lactamase activity from Escherichia coli strain J53 (R6K) was separated into two fractions by gel filtration. One fraction (F') had a well known molecular weight 21,000; the other (F) had a molecular weight greater than 70,000. The F beta-lactamase gave a fraction similar to F' after neuraminidase treatment followed by gel filtration, suggesting that beta-lactamase molecules may be associated with neuraminic acid-containing structures. Such complexes could be an explanation for the multiple bands given in isoelectrofocusing of crude enzymatic extracts.