Peptidyl dipeptidases (Ance and Acer) of Drosophila melanogaster: major differences in the substrate specificity of two homologs of human angiotensin I-converting enzyme.
Drosophila melanogaster angiotensin converting enzyme (Ance) and angiotensin converting enzyme related (Acer) are single domain homologs of mammalian peptidyl dipeptidase A (angiotensin I-converting enzyme) whose physiological substrates have not as yet been identified. We have investigated the in vitro substrate specificities of the two peptidases towards a variety of insect and mammalian peptides. Ance was generally much better than Acer at hydrolyzing peptides of 5-13 amino acids in length. Only two of the peptides, [Leu(5)]enkephalinamide and leucokinin-I were cleaved faster by Acer. Increasing NaCl concentration had opposite affects on the cleavage of [Leu(5)]enkephalin and [Leu(5)]enkephalinamide by Acer, decreasing the activity towards [Leu(5)]enkephalin but increasing the activity towards [Leu(5)]enkephalinamide. Of the insect peptides tested, the tachykinin-related peptide, Lom TK-1, proved to be the best substrate for Ance with a k(cat)/K(m) ratio of 0.122s(-1) microM(-1). However, in comparison, the D. melanogaster tachykinins, DTK-1, DTK-2, DTK-3 and DTK-4 were poor Ance substrates. DTK-5 was the best substrate of this family, but the apparent high K(m) for hydrolysis by Ance suggested that this peptide would not be a natural Ance substrate. This low affinity for DTK-5 is the likely reason why the peptide was not rapidly degraded in D. melanogaster hemolymph, where Ance was shown to be a major peptide-degrading activity.
Siviter
Richard J
RJ
Molecular and Cellular Biosciences Research, Faculty of Biological Sciences, University of Leeds, Miall Building, West Yorkshire LS2 9JT, UK.
Nachman
Ronald J
RJ
Dani
M Paulina
MP
Keen
Jeffrey N
JN
Shirras
Alan D
AD
Isaac
R Elwyn
RE
D000818:Animals; D029721:Drosophila Proteins; D004331:Drosophila melanogaster; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D007700:Kinetics; D008666:Metalloendopeptidases / Q000378:metabolism*; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity
D029721:Drosophila Proteins; C102762:Acer protein, Drosophila; C104431:Ance protein, Drosophila; D007703:Peptidyl-Dipeptidase A; D008666:Metalloendopeptidases