p.D70G/Y114H/S425P Asp70Gly/Tyr114His/Ser453Pro (p.D98G/Y142H/S453P Asp70Gly/Tyr114His/Ser425Pro in primary sequence with 28 amino-acids signal peptide) The Y114H(Y142H) and S425P(S453P) could be considered as natural but was only found in clones of neuroblastomas and gliostomas, as such are somatic mutations not found in families as abnormal plasma cholinesterases
Kinetic parameters
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References:
Title: Engineering of human cholinesterases explains and predicts diverse consequences of administration of various drugs and poisons. Schwarz M, Glick D, Loewenstein Y, Soreq H Ref: Pharmacol Ther, 67:283, 1995 : PubMed
Title: Intramolecular relationships in cholinesterases revealed by oocyte expression of site-directed and natural variants of human BCHE Neville LF, Gnatt A, Loewenstein Y, Seidman S, Ehrlich G, Soreq H Ref: EMBO Journal, 11:1641, 1992 : PubMed
Structure-function relationships of cholinesterases (CHEs) were studied by expressing site-directed and naturally occurring mutants of human butyrylcholinesterase (BCHE) in microinjected Xenopus oocytes. Site-directed mutagenesis of the conserved electronegative Glu441,Ile442,Glu443 domain to Gly441,Ile442,Gln443 drastically reduced the rate of butyrylthiocholine (BTCh) hydrolysis and caused pronounced resistance to dibucaine binding. These findings implicate the charged Glu441,Ile442,Glu443 domain as necessary for a functional CHE catalytic triad as well as for binding quinoline derivatives. Asp70 to Gly substitution characteristic of 'atypical' BCHE, failed to alter its Km towards BTCh or dibucaine binding but reduced hydrolytic activity to 25% of control. Normal hydrolytic activity was restored to Gly70 BCHE by additional His114 or Tyr561 mutations, both of which co-appear with Gly70 in natural BCHE variants, which implies a likely selection advantage for these double BCHE mutants over the single Gly70 BCHE variant. Gly70 BCHE variants also displayed lower binding as compared with Asp70 BCHE to cholinergic drugs, certain choline esters and solanidine. These effects were ameliorated in part by additional mutations or in binding solanidine complexed with sugar residues. These observations indicate that structural interactions exist between N' and C' terminal domains in CHEs which contribute to substrate and inhibitor binding and suggest a crucial involvement of both electrostatic and hydrophobic domains in the build-up of the CHE active center.
