Spectrofluorometric techniques have been employed to examine the active site of the terminal enzyme of the @entity1446 biosynthetic pathway, @entity70114 (protoheme ferrolyase, EC 4.99.1.1). The fluorescence of both endogenous @entity2340 and exogenous @entity54763 (MIANS) has been examined. The fluorescence emission of the enzyme's active site bound MIANS is at 428 nm while the enzyme @entity2340 (s) yielded a single fluorescence emission maximum at 347 nm. These values are characteristic of a polar environment for @entity2340 and a relatively nonpolar environment for the MIANS. The dynamic fluorescence quenching constants for @entity3323 of MIANS and @entity2340 are 3.00 M-1 and 1.85 M-1, respectively. Quenching constants for KI of both fluorescent centers were approximately 1 M-1. These data suggest that both fluorophores are poorly accessible to the external anionic contact quencher but that an unchanged quencher, while larger, is still better able to penetrate the enzyme's active site. The extrapolated anisotropies (r0) for @entity70114 -bound MIANS and @entity2340 are 0.198 and 0.307. The dissociation constant (KD) determined by fluorescence anisotropy of @entity7888 was 1.5 microM with the calculated number of @entity7170 binding sites as 1.0 per 40000 daltons. A model is presented for the active site of @entity70114 based upon the data presented here and previously. This model proposes that the active site is a hydrophobic pocket similar in nature to the @entity1446 binding crevices found in many hemoproteins.

Spectroscopic examination of the active site of bovine XXXX .

@entity70114 :: ('790571(Tax:9913)', 'Gene') :: ['ferrochelatase'] @entity7170 :: ('CHEBI:8337', 'Chemical') :: ['porphyrin'] @entity7888 :: ('CHEBI:15430', 'Chemical') :: ['protoporphyrin'] @entity3323 :: ('MESH:D020106', 'Chemical') :: ['acrylamide'] @entity2340 :: ('CHEBI:27897', 'Chemical') :: ['tryptophan'] @entity54763 :: ('MESH:C021310', 'Chemical') :: ['2-(4-maleimidylanilino)naphthalene-6-sulfonic acid'] @entity1446 :: ('MESH:D006418', 'Chemical') :: ['heme']
@entity70114 :: (790571(Tax:9913),Gene) :: ['ferrochelatase']
