PubMed Journals: Biochem Biophys Res Commun
Source: PMID: 9784398
⇦ ⇨ Biochem Biophys Res Commun. 1998 Sep
Gustin from human parotid saliva is carbonic
Thatcher BJ(1), Doherty AE, Orvisky E, Martin
BM, Henkin RI.
(1) Clinical Neuroscience Branch, NIMH,
NIH, Bethesda, Maryland, USA.
Gustin, a zinc-metalloprotein constituting
about 3% of human parotid saliva protein
was previously isolated and characterized
as a single polypeptide chain of 37kDa with
one mole of zinc tightly bound to the protein.
It exhibited biological activity activating
calmodulin dependent bovine brain cAMP
phosphodiesterase and was decreased in saliva
of patients with loss of taste in whom taste
buds showed a specific pathological morphology.
Determination of its primary structure by amino
acid sequence revealed it was identical
with carbonic anhydrase (CA) [EC 184.108.40.206]
VI and had two N-linked glycosylation sites.
Analysis by reverse phase HPLC and SDS-PAGE before
and after deglycosylation confirmed a single
peak with molecular weight of the purified
protein being 37kDa, the deglycosylated
protein, 33kDa. N-linked carbohydrate chains
contained N-acetyl glucosamine, galactose,
mannose, and fucose interior to di, tri
and tetra sialyated termini. By isoelectric
focusing five increasingly acidic pI values
were determined consistent with addition
of sialic acid as the terminal carbohydrate
residue on the N-linked glycoforms of the
protein. Gustin was found to exhibit CA
activity but was inhibited by known CA inhibitors
in a different manner than CA I or II. These
findings, consistent with analysis of previous
investigators, indicate that parotid saliva
gustin is CA VI.
Copyright 1998 Academic Press.
DOI: 10.1006/bbrc.1998.9356 PMID: 9784398
[Indexed for MEDLINE]