Amino acid compositions of carp kidney metallothionein

Abstract

In fish, homology on amino acid compositions of metallothionein (MT) between liver and kidney is not recognized. We previously reported the amino acid composition of carp hepato-pancreas MT [1]: in the present study amino acid composition of kidney MT was determined, and homology between them discussed. Twenty carps were injected intraperitoneally with 2 mg/kg body weight of Cd as CdCl 2 solution, daily for 3 days. On the fourth day t001 Amino Acid Composition of Carp Kidney and Hepato-pancreas. Amino acid Mol % (number) Carp Horse [2] Hepato-pancreas Kidney Kidney MT-I MT-II MT-I MT-II Lys 11.37(7) 10.09(6) 10.06(6) 10.09(6) 11.1(7) His - (0) - (0) - (0) - (0) - (0) Arg - (0) - (0) 0.51(0) 0.81(1) 1.9(1) Asp 8.47(5) 9.10(6) 8.04(5) 7.53(4) 5.0(3) Thr 7.10(4) 8.47(5) 6.68(4) 9.48(6) 1.81(1) Ser 11.23(7) 10.13(6) 6.99(4) 11.8(7) 11.9(8) Glu 3.11(2) 3.50(2) 5.40(3) 4.29(3) 4.7(1) Pro 4.89(3) 4.16(3) 3.55(2) 3.85(2) 2.9(2) Gly 10.64(6) 11.13(7) 9.30(6) 11.51(7) 9.2(5) Ala 5.82(3) 5.59(3) 8.43(5) 6.05(3) 11.6(7) Cys 34.24(20) 31.90(20) 32.70(21) 29.39(18) 33.9(20) Val 1.98(1) 2.35(1) 2.95(2) 2.98(2) 4.5(3) Met 1.01(1) 1.68(1) 0.96(1) 0.50(1) 1.5(1) He 0.11(0) 0.99(1) 1.67(1) 0.70(1) - (0) Leu (0) - (0) 2.74(2) 1.14(1) - (0) Tyr - (0) - (0) - (0) - (0) - (0) Phe - (0) - (0) - (0) - (0) - (0) the kidney was excised, treated successively by homogenization, ultracentrifugation, heating treatment, centrifugation, gel filtration (Sephadex G-75, Bio Gel P-10) and ion exchange chromatography (DEAE Sephadex A-25). By the gel filtration using Sephadex G-75, the Cd peak was observed, and it was estimated that this peak contained MT. By ion exchange chromatography this peak was separated into two fractions, having high concentration of Cd, and high absorption at 254 nm and no absorption at 280 nm respectively. The former fraction was named MT-I and the latter MT-II. By gel filtration using Bio-Gel P-10, a single Cd peak was observed in MT-I and MT-II, respectively. The molar ratio of Cd: Zn was 36:1 in MT-I and 27:1 in MT-II. Their purity was shown by polyacrylamide DISC-gel electrophoresis. The absorption at 254 nm in both MT fractions disappeared when they were brought to acidic condition. The amino acid compositions of carp kidney and hepato-pancreas are given in Table I. Cysteic content was about 30% in each organ. The contents of Lys, Glu, Pro and Met residues in carp MT were close to the values in mammal MT, but those of Thr and Ala residues were different. In kidney MT, some Leu residue was observed. Arginine residue was detected only in kidney MT-II. No aromatic amino acids and histidine residues were detected in carp MT. The amino acid compositions in kidney MT were little different from those of hepato-pancreas MT. Between MT-I and MT-II in kidney the contents of Thr, Ser, Ala and Cys residues were remarkably different.