Novel reactions catalysed by antibodies

New structural data on nonhydrolytic antibody catalysts gained over the pas t two years confirm that antibodies elicited against transition-state analo gues function by differential stabilisation of the transition-state over th e ground state through electrostatic, van der Waals, cation-pi and hydrogen -bonding interactions. The lack of chemical catalysis correlates with the l ow catalytic efficiency. Novel strategies that precisely position a key fun ctional residue in the antibody catalyst combining site have therefore emer ged, as demonstrated by crystallographic studies. Whereas antibodies with a bulky residue at position H100c of hypervariable loop H3 adopt different c avity shapes, other antibodies share a common deep combining site. This str uctural restriction might reflect the use of similar hydrophobic haptens to generate the antibody; novel hapten design or new immunisation strategies may, in the future, lead to more structurally diversified active sites.