EFFECTS OF ALCOHOLS ON THE HYDROLYSIS OF COLOMINIC ACID-CATALYZED BY STREPTOCOCCUS NEURAMINIDASE

Regulation of the activity of neuraminidase of Streptococcus sp. (grou p K) was evaluated by examining the effects of alcohols on the hydroly sis of colominic acids catalyzed by the neuraminidase, Two kinds of al cohol binding site, activation and inhibition sites, were proposed to exist, Competitive inhibition was observed with alcohols smaller than polyethylene glycol #300 (average molecular weight: 300), so the inhib ition site is considered to be the substrate binding site, the size of which was estimated to be 10 Angstrom in diameter. On the contrary, p olyethylene glycols larger than this size activated the enzyme by 1.5- 1.8 times, The activity could be raised by binding of the polyethylene glycols to the activation site. This activation was shown to be due s olely to the decrease in the Michaelis constant, K-m. The smaller poly ethylene glycols (#200 and #300) were also considered to bind to the a ctivation site, although activation was not clearly observed due to co mpensation with inhibition. Strong substrate inhibition by colominic a cid was also observed. The activity of Streptococcus neuraminidase was shown to be regulated intricately by the substrate colominic acid and alcohols contained in the reaction medium.