Lactoperoxidase haem, an iron-porphyrin thiol. |
| |
| Authors: | A W Nichol L A Angel T Moon P S Clezy |
| |
| Affiliation: | School of Applied Science, Riverina-Murray Institute of Higher Education, N.S.W., Australia. |
| |
| Abstract: | The haem prosthetic group of lactoperoxidase can be prepared from the enzyme in high yield by reductive cleavage with mercaptoethanol in 8 M-urea under mild conditions. The product yields porphyrins, after removal of iron, which show visible spectroscopic properties similar to protoporphyrin but are considerably more polar. In the presence of iodoacetamide, a different product is obtained by reductive cleavage. The proton n.m.r. and mass spectra of this compound indicate that the prosthetic group of the enzyme is the iron complex of 18-mercaptomethyl-2,7,12-trimethyl-3,8-divinylporphyrin-13,17-d ipropionic acid. It is proposed that the unusual strength of binding of the prosthetic group to the apoprotein is due to formation of a disulphide bond from a cysteine residue to the porphyrin thiol. |
| |
| Keywords: | |
|
|
