Bacillus subtilis HemY is a peripheral membrane protein essential for protoheme IX synthesis which can oxidize coproporphyrinogen III and protoporphyrinogen IX

• The hemY gene of the Bacillus subtilis hemEHY operon is essential for protoheme IX biosynthesis. Two previously isolated hemY mutations were sequenced. Both mutations are deletions affecting the hemY reading frame, and they cause the accumulation of coproporphyrinogen III or coproporphyrin III in the growth medium and the accumulation of trace amounts of other porphyrinogens or porphyrins intracellularly. HemY was found to be a 53-kDa peripheral membrane-bound protein. In agreement with recent findings by Dailey et al. (J. Biol. Chem. 269:813-815, 1994) B. subtilis HemY protein synthesized in Escherichia coli oxidized coproporphyrinogen III and protoporphyrinogen IX to coproporphyrin and protoporphyrin, respectively. The protein is not a general porphyrinogen oxidase since it did not oxidize uroporphyrinogen III. The apparent specificity constant, kcat/Km, for HemY was found to be about 12-fold higher with coproporphyrinogen III as a substrate compared with protoporphyrinogen IX as a substrate. The protoporphyrinogen IX oxidase activity is consistent with the function of HemY in a late step of protoheme IX biosynthesis, i.e., HemY catalyzes the penultimate step of the pathway. However, the efficient coproporphyrinogen III to coproporphyrin oxidase activity is unexplained in the current view of protoheme IX biosynthesis.

Ämnesord

NATURVETENSKAP  -- Biologi -- Mikrobiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Microbiology (hsv//eng)

Nyckelord

Porphyrinogens/*metabolism

Oxidation-Reduction

Mutation

Molecular Sequence Data

Membrane Proteins/biosynthesis/*genetics

Kinetics

Heme/*biosynthesis

Coproporphyrinogens/metabolism

Molecular

Cloning

Base Sequence

Amino Acid Sequence

Bacillus subtilis/*genetics/metabolism

Protoporphyrins/metabolism

Recombinant Fusion Proteins/biosynthesis

Sequence Analysis

DNA

Sequence Deletion

Species Specificity

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