Human brain leucyl aminopeptidase: isolation, characterization and specificity against some neuropeptides.
In order to obtain a greater understanding of the role of aminopeptidases in the degradation of peptides and proteins in the nervous system, we have isolated and characterized leucyl aminopeptidase (EC 3.4.11.1) from human cerebral cortex and studied its action on some physiologically important neuropeptides. The enzyme has a low specificity constant for the hydrolysis of Leu-7-amido-4-methylcoumarin (69s-1M-1) but the peptides Tyr-Gly-Gly and Tyr-Gly-Gly-Phe-Leu (Leu5-enkephalin) were much better substrates (specificity constants 8300 and 18050s -1M-1 respectively). Optimum activity for the degradation of Leu-enkephalin was obtained at pH10.5 in the presence of 5mM-Mn++. A sharp drop in specificity constant occurred with increasing chain length in the series Leu-enkephalin, dynorphin 1-8, 1-10 and 1-13, suggesting that the enzyme functions only as an oligopeptidase. Other neuropeptides were poor substrates (cholecystokinin octapeptide, angiotensin-I) or not hydrolysed at all (somatostatin, Arg8-vasopressin).
MRC Neurochemical Pathology Unit, Newcastle General Hospital, Newcastle upon Tyne, UK.
A M
AM
Gibson
J A
JA
Biggins
B
B
Lauffart
D
D
Mantle
J R
JR
McDermott
D000595:Amino Acid Sequence; D000804:Angiotensin II / Q000378:metabolism; D001127:Arginine Vasopressin / Q000378:metabolism; D002413:Cations, Divalent / Q000494:pharmacology; D002540:Cerebral Cortex / Q000201:enzymology*; D002852:Chromatography, Ion Exchange; D004399:Dynorphins / Q000378:metabolism; D004743:Enkephalin, Leucine / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007931:Leucyl Aminopeptidase / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000378:metabolism*; D012844:Sincalide / Q000378:metabolism; D013004:Somatostatin / Q000378:metabolism; D013379:Substrate Specificity
D002413:Cations, Divalent; D009479:Neuropeptides; D000804:Angiotensin II; D001127:Arginine Vasopressin; D013004:Somatostatin; D004743:Enkephalin, Leucine; D004399:Dynorphins; D007931:Leucyl Aminopeptidase; D012844:Sincalide