Lionel Grossbard

Abstract Rat tissues contain four hexokinases including both the liver-specific high Km glucokinase and three low Km hexo-kinases present in differing proportions in the various tissues. Each of the low Km hexokinase types designated I, II, and III has been purified approximately 150- to 400-fold from one or more rat tissues (Type I from brain and kidney, Type II from skeletal muscle and epididymal fat pad, and Type III from liver). Each purified enzyme type, regardless of tissue source, has certain unique properties that distinguish it from the other hexokinase types. The purified types retain their different electrophoretic and chromatographic properties as found in crude extracts. They also differ with respect to apparent Km values for glucose and probably for adenosine triphosphate, apparent Ki values for adenosine diphosphate and glucose 6-phosphate, and stability to heat and proteolytic inactivation. The different enzyme types are similar with respect to pH optimum, molecular weight, hexose and nucleotide specificities, Km for fructose, and the qualitative nature of inhibition by ADP and glucose-6-P. The available evidence indicates that these hexokinase types represent different molecular forms and are not artifacts of preparation.

We have described an IgM antibody from a patient with macroglobulinemia specifically reacting with poly-alpha(2----8)N-acetyl neuraminic acid (NeuNAc) the capsular polysaccharide of two important human pathogens, group B meningococcus and E. coli K1. This antibody has a narrowly defined specificity in its interactions with polysaccharides, being unable to bind poly-alpha(2----9)NeuNAc or alternating poly-alpha(2----8)alpha(2----9)NeuNAc. However, it shows interesting crossreactivity with seemingly unrelated polynucleotides and denatured DNA, supporting the hypothesis that charged groups with a given spacing may determine the specificity of antigen-antibody interactions on otherwise dissimilar molecular structures. Despite the crossreactivity with denatured DNA and polynucleotides, the antibody does not appear to have adverse effects in the patient. The antibody protects newborn rats against E. coli K1 infection, as well as the standard horse antiserum H46, and one would expect it to prove useful in humans as an adjunct to antibiotic therapy in infections with group B meningococcus and E. coli K1. We have attempted to clone the antibody-producing cells from peripheral blood, and have shown that the relevant cells are present and can be cultured.