Evidence for 'lock and key' character in an anti-phosphonate hydrolytic antibody catalytic site augmented by non-reaction centre recognition: variation in substrate selectivity between an anti-phosphonate antibody, an anti-phosphate antibody and two hydrolytic enzymes.
The substrate selectivities of an anti-phosphonate and an anti-phosphate kinetically homogeneous polyclonal catalytic antibody preparation and two hydrolytic enzymes were compared by using hapten-analogous and truncated carbonate and ester substrates each containing a 4-nitrophenolate leaving group. Syntheses of the truncated substrates devoid of recognition features in the non-leaving group parts of the substrates are reported. The relatively high kinetic selectivity of the more active anti-phosphonate antibody preparation is considered to depend on a relatively rigid catalytic site with substantial reaction centre specificity together with other important recognition interactions with the extended non-leaving group part of the substrate. In contrast, the less catalytically active, more flexible anti-phosphate antibody exhibits much lower kinetic selectivity for the substrate reaction centre comparable with that of the hydrolytic enzymes with activity much less dependent on recognition interactions with the non-leaving group part of the substrate. The ways in which haptenic flexibility and IgG architecture might contribute to the differential kinetic selectivities are indicated.
Sonkaria
Sanjiv
S
Laboratory of Structural and Mechanistic Enzymology, School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
Boucher
Guillaume
G
Flórez-Olvarez
José
J
Said
Bilal
B
Hussain
Syeed
S
Ostler
Elizabeth L
EL
Gul
Sheraz
S
Thomas
Emrys W
EW
Resmini
Marina
M
Gallacher
Gerard
G
Brocklehurst
Keith
K
D000818:Animals; D017151:Antibodies, Catalytic / Q000737:chemistry* / Q000378:metabolism*; D000915:Antibody Affinity; D000937:Antigen-Antibody Reactions; D001666:Binding Sites, Antibody; D020134:Catalytic Domain; D002417:Cattle; D002918:Chymotrypsin / Q000378:metabolism; D004950:Esterases / Q000378:metabolism; D006867:Hydrolases / Q000378:metabolism; D006868:Hydrolysis; D008099:Liver / Q000201:enzymology; D008958:Models, Molecular; D063065:Organophosphonates / Q000138:chemical synthesis / Q000276:immunology*; D010179:Pancreas / Q000201:enzymology; D010710:Phosphates / Q000138:chemical synthesis / Q000276:immunology*; D013379:Substrate Specificity; D013552:Swine; D014614:Vaccines, Synthetic / Q000737:chemistry / Q000276:immunology / Q000378:metabolism
D017151:Antibodies, Catalytic; D063065:Organophosphonates; D010710:Phosphates; D014614:Vaccines, Synthetic; D006867:Hydrolases; D004950:Esterases; D002918:Chymotrypsin; C117608:alpha-chymotrypsin