caa a22 4500 477132669 CHVBK 20180405111708.0 cr unu---uuuuu 170330e19970601xx s 000 0 eng 10.1023/A:1018383207608 doi (NATIONALLICENCE)springer-10.1023/A:1018383207608 L¿vstad Rolf Department of Medical Biochemistry, University of Oslo, Oslo, Norway aut A study on ascorbate inhibition of ceruloplasmin ferroxidase activity [Elektronische Daten] [Rolf L¿vstad] The ferroxidase activity of ceruloplasmin is often determined according to the method of Johnson et al. (1967), using apotransferrin for trapping ferric ions generated by the enzyme; spectrophotometrically monitoring the Fe-transferrin formation at pH6.0. Reports have shown that ascorbate inhibits this reaction, and it is hypothesized that the effect could be of physiological significance in individuals with a high ascorbate to ceruloplasmin ratio in plasma (e.g. premature babies). The present study shows that the inhibitory effect of ascorbate rapidly decreases with increasing pH. At pH7.4 no significant effect was observed, the result suggesting that ascorbate is not a physiological inhibitor of ceruloplasmin. Furthermore, experiments demonstrate that at acidic pH the inhibitory effect of ascorbate on the rate of Fe-transferrin formation is not primarily due to an interaction with ceruloplasmin, but to a reduction of enzymically generated ferric ions before they are bound to apotransferrin. Chapman and Hall, 1997 ascorbate nationallicence ceruloplasmin nationallicence conalbumin nationallicence iron ions nationallicence transferrin nationallicence Biometals Kluwer Academic Publishers 10/2(1997-06-01), 123-126 0966-0844 10:2<123 1997 10 10534 https://doi.org/10.1023/A:1018383207608 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1018383207608 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- L¿vstad Rolf Department of Medical Biochemistry, University of Oslo, Oslo, Norway aut NATIONALLICENCE 773 0- Biometals Kluwer Academic Publishers 10/2(1997-06-01), 123-126 0966-0844 10:2<123 1997 10 10534 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer