Chemical modification and pH dependence of kinetic parameters to identify functional groups in a glucosyltransferase from Strep. Mutans

Conference · Thu May 01 00:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5220480

Bell, J E; Leone, A; Bell, E T

A glucosyltransferase, forming a predominantly al-6 linked glucan, was partially purified from the culture filtrate of S. mutans GS-5. The kinetic properties of the enzyme, assessed using the transfer of /sup 14/C glucose from sucrose into total glucan, were studied at pH values from pH 3.5 to 6.5. From the dependence of km on pH, a group with pKa = 5.5 must be protonated to maximize substrate binding. From plots of V/sub max/ vs pH two groups, with pKa's of 4.5 and 5.5 were indicated. The results suggest the involvement of either two carboxyl groups (one protonated, one unprotonated in the native enzyme) or a carboxyl group (unprotonated) and some other protonated group such as histidine, cysteine. Chemical modification studies showed that Diethylyrocarbonate (histidine specific) had no effect on enzyme activity while modification with p-phydroxy-mercuribenzoate or iodoacetic acid (sulfhydryl reactive) and carbodimide reagents (carboxyl specific) resulted in almost complete inactivation. Activity loss was dependent upon time of incubation and reagent concentration. The disaccharide lylose, (shown to be an inhibitor of the enzyme with similar affinity to sucrose) offers no protection against modification by the sulfhydryl reactive reagents.

• Research Organization: Univ. of Rochester Medical Center, NY
• OSTI ID: 5220480
• Report Number(s): CONF-8606151-
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
GLYCOSYL TRANSFERASES
BIOCHEMICAL REACTION KINETICS
PURIFICATION
CARBON 14 COMPOUNDS
ENZYME ACTIVITY
ENZYME INHIBITORS
GLUCOSE
PH VALUE
REAGENTS
STREPTOCOCCUS
TRACER TECHNIQUES
ALDEHYDES
BACTERIA
CARBOHYDRATES
ENZYMES
HEXOSES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MICROORGANISMS
MONOSACCHARIDES
ORGANIC COMPOUNDS
REACTION KINETICS
SACCHARIDES
TRANSFERASES
550201* - Biochemistry- Tracer Techniques