Evidence for 54-kD protein in chicken kidney as a cytochrome P450 with a high molecular activity of 25-hydroxyvitamin D3 1 alpha-hydroxylase.
Gerontology
; 42 Suppl 1: 67-77, 1996.
Article
in En
| MEDLINE
| ID: mdl-8964524
ABSTRACT
Conversion of 25-hydroxyvitamin D3 (25(OH)D3) to the active vitamin D3, 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3) is catalyzed by 25(OH)D3, 1 alpha-hydroxylase(1 alpha-hydroxylase). It has been suggested that this enzyme is cytochrome P450 (P450). We purified 1 alpha-hydroxylase 430-fold from cholate-solubilized kidney mitochondria of vitamin D-deficient chickens by utilizing hydrophobic and ion-exchange column chromatographies. Enzymatic activity was assessed by measuring on HPLC the formation of 1 alpha,25(OH)2D3 from 25(OH)D3 in the assay mixture containing NADPH, adrenodoxin reductase, adrenodoxin as a reducing system. The purified enzyme showed a CO-difference spectrum characteristic of P450. The molecular activity of this preparation was calculated to be 8.7 pmol/min/pmol P450. This value was higher by more than 87-fold than those reported so far. The present preparation was found to contain several proteins on SDS-PAGE. Among them, only the 54-kD protein became undetectable when kidney mitochondria from normal and vitamin D-replete chickens, where 1 alpha-hydroxylase activities were 15 and 0% of that found in vitamin D-deficient chicken, respectively, were used as the starting enzyme sources. Furthermore, the band intensity of the 54-kD protein accounted for the spectrophotometrically determined amount of P450 in the preparation. These results suggest that the 54-kD protein is 1 alpha-hydroxylase.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Cytochrome P-450 Enzyme System
/
25-Hydroxyvitamin D3 1-alpha-Hydroxylase
/
Kidney
Limits:
Animals
Language:
En
Journal:
Gerontology
Year:
1996
Document type:
Article
Affiliation country:
Japón