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      Heme oxygenase: function, multiplicity, regulatory mechanisms, and clinical applications

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      The FASEB Journal
      Wiley

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          Abstract

          In biological systems oxidation of heme is carried out by two isozymes of the microsomal heme oxygenase, HO-1 and HO-2. HO-1 is the commonly known heme oxygenase, the activity of which can be induced by up to 100-fold in response to a wide variety of stimuli (metals, heme, hormones, etc.). HO-2 was only recently discovered, and the isozyme appears to be uninducible. The two forms are products of two different genes and differ in their tissue expression. The primary structure of HO-1 and an HO-2 fragment of 91 amino acid residues show only 58% homology, but share a region with 100% secondary structure homology. This region is believed to be the catalytic site. Most likely, HO-1 gene is regulated in the same manner as metallothione in the gene. HO-1 has a heat shock regulatory element, and possibly many promoter elements, which bind to respective inducers and cause transcription of the gene. In vivo induction of HO-1 activity in the liver is accompanied by decreases in the total P-450 levels and, in a reconstituted system, cytochrome P-450b heme can be quantitatively converted to biliverdin by HO-1 and HO-2. The enzyme activity is inhibited in vivo for extended periods subsequent to binding of Zn- and Sn- protoporphyrins. This property appears useful for the suppression of bilirubin production. The metalloporphyrins, however, are not innocuous and cause major disruptions in cellular metabolism. In this review recent findings on heme oxygenase are highlighted.

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          Author and article information

          Journal
          The FASEB Journal
          FASEB j.
          Wiley
          0892-6638
          1530-6860
          July 1988
          July 1988
          July 1988
          July 1988
          : 2
          : 10
          : 2557-2568
          Affiliations
          [1 ]Department of BiophysicsUniversity of Rochester School of MedicineRochesterNew York14642USA
          Article
          10.1096/fasebj.2.10.3290025
          3290025
          6e68a6c1-d9b7-45cb-ac77-42ccb5de7653
          © 1988

          http://onlinelibrary.wiley.com/termsAndConditions#vor

          http://doi.wiley.com/10.1002/tdm_license_1.1

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