The hydrolysis of brain and atrial natriuretic peptides by porcine choroid plexus is attributable to endopeptidase-24.11.
The hydrolysis of the porcine 26-residue brain natriuretic peptide (BNP-26) and its counterpart human 28-residue atrial natriuretic peptide (alpha-hANP) by pig membrane preparations and purified membrane peptidases was studied. When the two peptides were incubated with choroid plexus membranes, the products being analysed by h.p.l.c., alpha-hANP was degraded twice as fast as BNP. The h.p.l.c. profiles of alpha-hANP hydrolysis, in short incubations with choroid plexus membranes, yielded alpha hANP' as the main product, this having been previously shown to be the result of hydrolysis at the Cys7-Phe8 bond. In short incubations this cleavage was inhibited 84% by 1 microM-phosphoramidon, a specific inhibitor of endopeptidase-24.11. BNP-26 was hydrolysed by choroid plexus membranes, kidney microvillar membranes and purified endopeptidase-24.11 in a manner that yielded identical h.p.l.c. profiles. In the presence of phosphoramidon, hydrolysis by the choroid plexus membranes was 94% inhibited. Captopril had no effect and, indeed, no hydrolysis of BNP-26 by peptidyl dipeptidase A (angiotensin-converting enzyme) was observed even after prolonged incubation with the purified enzyme. The stepwise hydrolysis of BNP-26 by endopeptidase-24.11 was investigated by sequencing the peptides produced during incubation. The initial product resulted from hydrolysis at Ser14-Leu15, thereby opening the ring. This product (BNP') was short-lived; further degradation involved hydrolysis at Ile12-Gly13, Arg8-Leu9, Gly17-Leu18, Val22-Leu23, Arg11-Ile12 and Cys4-Phe5. Thus endopeptidase-24.11 is the principal enzyme in renal microvillar and choroid plexus membranes hydrolysing BNP-26 and alpha-hANP.
Bourne
A
A
Department of Biochemistry, University of Leeds, U.K.
Kenny
A J
AJ
D000595:Amino Acid Sequence; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D002831:Choroid Plexus / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D006020:Glycopeptides / Q000494:pharmacology; D006868:Hydrolysis; D007668:Kidney / Q000201:enzymology; D008969:Molecular Sequence Data; D020097:Natriuretic Peptide, Brain; D015260:Neprilysin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D013552:Swine
D006020:Glycopeptides; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D020097:Natriuretic Peptide, Brain; D009320:Atrial Natriuretic Factor; D015260:Neprilysin; C008890:phosphoramidon