Serologic Characteristics of Glucokinases from Entamoeba histolytica and Related Species1

Abstract

SYNOPSIS. An enzyme inhibition technic was employed for quantitative comparison of the serologic properties of glucokinases from 4 groups of amebas which are structurally indistinguishable species: Entamoeba histolytica, E. moshkovskii, E. invadens and E. terrapinae. Antiglucokinase was prepared by immunizing rabbits with crude extracts of DKB and Laredo strains of E. histolytica. The combination of amebal glucokinase and homologous antibody was a pseudoirreversible reaction. The inhibition was proportional to the amount of antibody until at least 60% of the enzyme was inhibited, and the inhibition was 96–92% in the region of antibody excess. The nature of the inhibition was uncompetitive with respect to substrate. The presence of substrate had no effect upon the inhibition. Anti‐DKB glucokinase inhibited equally glucokinases from DKB, JH, K9, 200, NRS, BH, JI, F22, and N strains. Anti‐Laredo glucokinase equally inhibited glucokinases from Laredo, Huff, JA, AG, and 403 strains; 2.5–2.9 times as much antiserum was required to produce the same degree of inhibition between antisera and strains of heterologous group as with homologous antigen. Anti‐DKB and anti‐Laredo glucokinases cross‐reacted with the enzyme from E. moshkovskii, but not with enzymes from reptilian amebas. A new glucokinase‐anti‐glucokinase dissociation test was developed which provides a method for qualitative differentiation of antiglucokinase against DKB strain from anti‐glucokinase against Laredo strain.