974
BIOCHEMICAL SOCIETY TRANSACTIONS
mol.wts. of 12000 and 25000 for fractions C1 and C2 respectively. After treatment of the citrate-extracted membrane fraction with sodium dodecyl sulphate, eight fucosylglycoprotein bands were identified, with mol.wts. of approx. 140000, 135000, 115000, 850oG,70000,40000, 31 000 and 27000. The remaining pellet was then incubated with papain (EC 3.4.22.2) and the hydrolysate chromatographed on DEAE-cellulose. A single fucosylglycopeptide fraction was resolved (fraction D), which accounted for 12% of the total [3Hlfucose incorporated into the synaptic-membrane preparation. Preliminary chemical analysis of fraction D has indicated that carbohydrate component is also rich in sialic acid and hexosamine. There is evidence that attachment of carbohydrates occurs in the nerve cell body and that glycoproteins are transported rapidly along the axon to the nerve terminal (Bennett et al., 1973). However, glycosyltransferases associated with glycoprotein synthesis have been detected in synaptosomes (Festoff et al., 1971). It could be postulated that the low-molecular-weight fucosylglycoproteins previously identified (Branford White & Moseby, 1979)may be precursors of the synaptic-membrane glycoproteins characterized in the present study. Bennett, G., Di Giamberardino, L., Koenig, H. L. & Droz, €3. (1973) Bruin Rrs. 60,129-146 Branford White, C. J. & Moseby, A. M. (1979) Biuchem. Soc. Trans. 7 , 2 6 2 7 Brunngraber, E. G. (1972) Ado. Exp. Men. Bid. 32,109-133 Burgoyne, R. D. & Rose, S. P. R. (1978) Biochem. Suc. Truns. 6 , 1025--1026 Cotman, C. W. R: Matthews, D. A. (1971) Biuchini. Biuphys. Acfu249, 380-394 Festoff, B. W., Appel, S. H. &Day, E. (1971)J. Neuruchem. 18, 1871-1880 Krusius, T. & Finne, J. (1978) Eur. J. Biochem. 84,395-403 Margolis, R. K. & Margolis, R. E. (1972) 1.Nwrochenq. 19, 1023-1030 Zatz, M. & Barondes, S. H. (1970) J. Neurochem. 17, 157-163
Variability of Lipid Concentrations and Phosphatidylcholine-Cholesterol Acyltransferase Activity in Plasma from Three Species of Amphibians MICHAEL P. T. GILLETT, ANA M. K. SIBRIAN and JAMES S . OWEN* Departamento de Bioquimica, Centro de Ci2ncias Bioldgicas, Universidade Federal de Pernambuco, Recife-PE, Brazil
Phosphatidylcholine-cholesterol acyltransferase (EC 2.3.1.43, hereafter called ‘acyltransferase’) plays an important role in the metabolism of plasma lipoproteins and has been extensively studied in man (Glomset, 1968; Glomset & Norum, 1973). The enzyme has also been described in plasma from several species of mammals (Noble et al., 1972; Stokke, 1974; Lacko et al., 1974) and, morerecently, in reptiles and amphibians(Gillett, 1978). In human plasma, one important aspect of the physiological role of the acyltransferase may be in the removal of the free cholesterol and phosphatidylcholine that appear necessary to transport triacylglycerol, as either very-low-density lipoprotein or chylomicrons (Schumaker & A d a m , 1969). After hydrolysis of the lipoprotein triacylglycerol, the excess surface coat of free cholesterol and phosphatidylcholine and some apoproteins are transferred to high-density lipoproteins, which are then suitable substrates for the acyltransferase (Glomset & Norum, 1973). The good correlation between human acyltransferase activity and plasma triacylglycerol concentration (Blomhoff, 1974; Wallentin & Vikrot, 1975; Gillett et al., 1978) has been discussed as a further indication of an indirect role for the enzyme in triacylglycerol transport and metabolism. In the present communication the variation of acyltransferase activity in relation to plasma triacylglycerol concentration is described for three species of amphibians. Adult specimens of the frog Rana palmipes and the toads Bufo granulosus and Bufo marinus were collected from the wild at Recife (Northeast Brazil) and plasma samples *Present address: Department of Biochemistry and Chemistry, Royal Free Hospital School of Medicine, University of London, 8 Hunter Street, London WClN IBP, U.K. 1979
583rd MEETING, CAMBRIDGE
975
Table 1. Range of plasma lipid concentrations and phosphatidylcholine-cholesterol acyltransferase activity in three species of amphibians Correlation coefficients between acyltransferase activity and lipid concentrations are given in parentheses and significant values are indicated (*P
BIOCHEMICAL SOCIETY TRANSACTIONS
mol.wts. of 12000 and 25000 for fractions C1 and C2 respectively. After treatment of the citrate-extracted membrane fraction with sodium dodecyl sulphate, eight fucosylglycoprotein bands were identified, with mol.wts. of approx. 140000, 135000, 115000, 850oG,70000,40000, 31 000 and 27000. The remaining pellet was then incubated with papain (EC 3.4.22.2) and the hydrolysate chromatographed on DEAE-cellulose. A single fucosylglycopeptide fraction was resolved (fraction D), which accounted for 12% of the total [3Hlfucose incorporated into the synaptic-membrane preparation. Preliminary chemical analysis of fraction D has indicated that carbohydrate component is also rich in sialic acid and hexosamine. There is evidence that attachment of carbohydrates occurs in the nerve cell body and that glycoproteins are transported rapidly along the axon to the nerve terminal (Bennett et al., 1973). However, glycosyltransferases associated with glycoprotein synthesis have been detected in synaptosomes (Festoff et al., 1971). It could be postulated that the low-molecular-weight fucosylglycoproteins previously identified (Branford White & Moseby, 1979)may be precursors of the synaptic-membrane glycoproteins characterized in the present study. Bennett, G., Di Giamberardino, L., Koenig, H. L. & Droz, €3. (1973) Bruin Rrs. 60,129-146 Branford White, C. J. & Moseby, A. M. (1979) Biuchem. Soc. Trans. 7 , 2 6 2 7 Brunngraber, E. G. (1972) Ado. Exp. Men. Bid. 32,109-133 Burgoyne, R. D. & Rose, S. P. R. (1978) Biochem. Suc. Truns. 6 , 1025--1026 Cotman, C. W. R: Matthews, D. A. (1971) Biuchini. Biuphys. Acfu249, 380-394 Festoff, B. W., Appel, S. H. &Day, E. (1971)J. Neuruchem. 18, 1871-1880 Krusius, T. & Finne, J. (1978) Eur. J. Biochem. 84,395-403 Margolis, R. K. & Margolis, R. E. (1972) 1.Nwrochenq. 19, 1023-1030 Zatz, M. & Barondes, S. H. (1970) J. Neurochem. 17, 157-163
Variability of Lipid Concentrations and Phosphatidylcholine-Cholesterol Acyltransferase Activity in Plasma from Three Species of Amphibians MICHAEL P. T. GILLETT, ANA M. K. SIBRIAN and JAMES S . OWEN* Departamento de Bioquimica, Centro de Ci2ncias Bioldgicas, Universidade Federal de Pernambuco, Recife-PE, Brazil
Phosphatidylcholine-cholesterol acyltransferase (EC 2.3.1.43, hereafter called ‘acyltransferase’) plays an important role in the metabolism of plasma lipoproteins and has been extensively studied in man (Glomset, 1968; Glomset & Norum, 1973). The enzyme has also been described in plasma from several species of mammals (Noble et al., 1972; Stokke, 1974; Lacko et al., 1974) and, morerecently, in reptiles and amphibians(Gillett, 1978). In human plasma, one important aspect of the physiological role of the acyltransferase may be in the removal of the free cholesterol and phosphatidylcholine that appear necessary to transport triacylglycerol, as either very-low-density lipoprotein or chylomicrons (Schumaker & A d a m , 1969). After hydrolysis of the lipoprotein triacylglycerol, the excess surface coat of free cholesterol and phosphatidylcholine and some apoproteins are transferred to high-density lipoproteins, which are then suitable substrates for the acyltransferase (Glomset & Norum, 1973). The good correlation between human acyltransferase activity and plasma triacylglycerol concentration (Blomhoff, 1974; Wallentin & Vikrot, 1975; Gillett et al., 1978) has been discussed as a further indication of an indirect role for the enzyme in triacylglycerol transport and metabolism. In the present communication the variation of acyltransferase activity in relation to plasma triacylglycerol concentration is described for three species of amphibians. Adult specimens of the frog Rana palmipes and the toads Bufo granulosus and Bufo marinus were collected from the wild at Recife (Northeast Brazil) and plasma samples *Present address: Department of Biochemistry and Chemistry, Royal Free Hospital School of Medicine, University of London, 8 Hunter Street, London WClN IBP, U.K. 1979
583rd MEETING, CAMBRIDGE
975
Table 1. Range of plasma lipid concentrations and phosphatidylcholine-cholesterol acyltransferase activity in three species of amphibians Correlation coefficients between acyltransferase activity and lipid concentrations are given in parentheses and significant values are indicated (*P
