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Avian hepatic T3 generation by 5'-monodeiodination: characterization of two enzymatic pathways and the effects of goitrogens.

Authors
  • McNabb, F M
  • Lyons, L J
  • Hughes, T E
Type
Published Article
Journal
Comparative Biochemistry and Physiology Part A Physiology
Publisher
Elsevier
Publication Date
Jan 01, 1986
Volume
85
Issue
2
Pages
249–255
Identifiers
PMID: 2876833
Source
Medline
Language
English
License
Unknown

Abstract

The enzymatic nature of 5'-monodeiodination (5'-D) in avian liver homogenates was demonstrated by abolishment of activity by iopanoic acid (IOP). T3 production from T4 was dependent on enzyme and substrate concentrations, incubation time, incubation temperature, and pH. Two pathways of 5'-D activity were present in avian liver and exhibited characteristics similar to those described in mammalian tissues. Type II activity was identified as propylthiouracil (PTU)-insensitive activity. Type I (PTU-sensitive) was determined by difference between Total and Type II. Km values were 1.58 microM T4 for Total activity and 0.90 nM T4 for Type II, corresponding to the characteristics of the mammalian pathways. The effects of goitrogens on avian hepatic 5'-D were equivalent to those reported for the mammalian enzyme.

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