Fructose 1,6-diphosphate aldolase of Drosophila melanogaster: comparative sequence analyses of the cysteine-containing peptides

Fructose-1,6-bisphosphate aldolase from Drosophila melanogaster: primary structure analysis, secondary structure prediction, and comparison with vertebrate aldolases

The amino acid sequence of fructose-1,6-bisphosphate aldolase from Drosophila melanogaster was determined and was compared with those of five vertebrate aldolases on record. The four identical polypeptide chains of the insect enzyme, acetylated at the N-terminus and three residues shorter than the vertebrate chains, contain 360 amino acid residues. Of these 190 (or 53%) are identical in all six enzymes and in addition 33 positions (or 9%) are occupied by homologous residues. Comparison with the muscle-type isoaldolases from man and rabbit and the liver-type isoaldolases from man, rat, and chicken indicates an average sequence identity of 70 and 63%, respectively. Thus, the insect and the vertebrate muscle aldolases are probably coded by orthologous genes. On this basis an average rate of evolution of 3.0 PAM per 10(8) years is calculated, documenting an evolutional divergence slower than that of cytochrome c (4.2 PAM/10(8) years). The rate is also lower than that of the liver isoform (3.6 PAM/10(8) years). Secondary structure prediction analysis for Drosophila aldolase suggests the occurrence of 11-12 helical segments and 8-9 beta-strands. The conspicuous alternation of these structures in all six aldolases, especially in the C-terminal 200 residues, is consistant with the formation of an alpha beta-barrel supersecondary structure as documented for several other glycolytic enzymes.

Re-evaluation of the role of thiol groups in rabbit muscle aldolase A

Exposed thiol groups of rabbit muscle aldolase A were modified by 5,5'-dithiobis(2-nitrobenzoic) acid with concomittant loss of enzyme activity. When 5-thio-2-nitrobenzoate residues bound to enzyme SH groups were replaced by small and uncharged cyanide residues the enzyme activity was restored by more than 50%. The removal of a bulky C-terminal tyrosine residue from the active site of aldolase A resulted in enzyme which was inhibited by 5,5'-dithiobis(2-nitrobenzoic) acid only by 50% and its activity was nearly unchanged after modification of its thiol groups with cyanide. The results obtained show directly that rabbit muscle aldolase A does not possess functional cysteine residues and that the inactivation of the enzyme caused by sulfhydryl group modification reported previously can be attributed most likely to steric hindrance of a catalytic site by modifying agents.

Amino acid sequence of an invertebrate FBP aldolase (from Drosophila melanogaster)

The complete amino acid sequence of FBP aldolase from Drosophila melanogaster has been determined. The enzyme contains four identical subunits of 360 amino acid residues. The primary structure of the monomer was established using automated Edman degradation on fragments prepared by CNBr-cleavage, by partial acid cleavage at the unique Asp-Pro bond and by oxidative cleavage at the three tryptophan residues. Manual Edman-Chang degradation was used on smaller peptides obtained by digestion with Staphylococcus aureus V8 protease, trypsin or chymotrypsin. The primary structure of Drosophila aldolase exhibits very extensive homology with the sequence of rabbit muscle aldolase (71% identity), thus explaining the early observation that Drosophila and mammalian aldolases form active interspecies hybrid quaternary structures (Brenner-Holzach, O. and Leuthardt, F., Eur. J. Biochem. (1972) 31, 423-426).