Antisera probes to an atypical pseudocholinesterase from surgeonfish reveal immunochemical variability and tissue‐specific molecular polymorphism

Abstract

Polyclonal antisera were raised in rabbits against the purified sialated, presumed-globular tetrameric pseudocholinesterase (pseudo-ChE) from surgeonfish (Leibel: Journal of Experimental Zoology 1988b) and against commercially obtained Electrophorus electroplax AChE. The resulting antisera probes were absolutely specific for their respective antigens and failed to titrate ChE activities heterologously. However, each antisera probe did crossreact with its other respective globular and asymmetric aggregational isozymes. The resultant specific probes were then used to examine interspecific evolutionary conservation of the two ChE activities and, in conjunction with velocity sedimentation analysis and differential paraoxon inhibition, the tissue distribution and molecular polymorphism of these same two enzyme systems in surgeonfish. These experiments suggest the tight evolutionary conservation of AChE in contrast to the apparent high variability of pseudo-ChE amongst the wide range of teleost fishes tested. The native atypical pseudo-ChE was shown to exist, like AChE, as a series of sialated and asialated globular and asymmetric aggregational isozymes whose relative distribution exhibits marked tissue specificity. The extremely high levels of pseudo-ChE characteristic of white skeletal (epaxial) muscle, in particular, was conspicuous, and its occurrence in the sarcolemma is discussed in the context of its possible function and in relation to the apparent lack of evolutionary conservation amongst marine teleosts.

Evolution of Acetylcholinesterase and Butyrylcholinesterase in the Vertebrates: An Atypical Butyrylcholinesterase from the Medaka Oryzias latipes

“…Splice variant data are from Leibel [20].eData are from Davies et al [100].fData are from Ucar et al [101].gData are from Loewenstein-Lichtenstein et al; IC 50 was back calculated from a calculated K i [69].hData are from Blong et al [37].iA, acetylthiocholine; P, propionylthiocholine; B, butyrylthiocholine; +, inhibition by high substrate concentrations; -, no inhibition; substrate activation is not considered.jN.M., not measureable.kN.D., not determined.lSplice variant determined by molecular forms present and sequence data when available.…”

“…The atypical BChE of P. flesus is also a GPI-anchored G 2 a [19]. However, the atypical BChEs from T. marmorata and A. dussumieri are BChE T types since they are capable of assembling into G 1 , G 2 , and G 4 molecular forms, and are able to interact with the collagenic tail protein ColQ [17], [20]. The forms of the P. platessa enzyme are not known.…”

“…Although the dichotomy between AChE and BChE is generally clear in birds and mammals [1], [15], [16], the two enzymes often more closely resemble one another functionally in fish. In the cartilaginous fish, the electric ray Torpedo marmorata [17], and the bony fishes, the plaice Pleuronectes platessa [18], the flounder Platichthys flesus [19], and perhaps the surgeonfish Acanthuras dussumieri [20], [21], ChEs with properties intermediate to and atypical of AChE and BChE are found along with AChE. These enzymes have alternatively been considered atypical ChEs [18], [19] or atypical pseudo-cholinesterases (pseudo-ChEs) [17], [20]; we are designating them as atypical BChEs, as suggested by Whittaker [22].…”

“…However, according to the Xenopus tropicalis genome project [38] and other evidence [34], [39]–[42], an H variant of BChE appears to be present in amphibian Xenopus species. The atypical BChEs of T. marmorata and A. dussumieri are T variants (BChE T ), assembling a collection of globular and asymmetric forms [17], [20]. In remarkable contrast, the atypical BChE of P. flesus is BChE H , assembling only into GPI-anchored G 2 a forms [19].…”

Zebrafish Acetylcholinesterase Is Encoded by a Single Gene Localized on Linkage Group 7

“…18). The situation is less clear in bony fish because a BChE or pseudocholinesterase activity is found in some perciform fish as follows: flounder, sea bass, and surgeon fish (35,36). A BChE activity was clearly demonstrated in gymnote brain (37).…”