This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Weinstein, J. D. Articles by Beale, S. I. Search for Related Content PubMed PubMed Citation Articles by Weinstein, J. D. Articles by Beale, S. I. Agricola Articles by Weinstein, J. D. Articles by Beale, S. I.

Articles

Biosynthesis of Protoheme and Heme a Precursors Solely from Glutamate in the Unicellular Red Alga Cyanidium caldarium¹

Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912

Two biosynthetic routes to the heme, chlorophyll, and phycobilin precursor, -aminolevulinic acid (ALA) are known: conversion of the intact five-carbon skeleton of glutamate, and ALA synthase-catalyzed condensation of glycine plus succinyl-coenzyme A. The existence and physiological roles of the two pathways in Cyanidium caldarium were assessed in vivo by determining the relative abilities of [2-¹⁴C]glycine and [1-¹⁴C]glutamate to label protoheme and heme a. Glutamate was incorporated to a much greater extent than glycine into both protoheme and heme a, even in cells that were unable to form chlorophyll and phycobilins. The small incorporation of glycine could be accounted for by transfer of label to intracellular glutamate pools, as determined from amino acid analysis. It thus appears that C. caldarium makes all tetrapyrroles, including mitochondrial hemes, solely from glutamate, and there is no contribution by ALA synthase in this organism.

This article has been cited by other articles:

				E. D. von Gromoff, A. Alawady, L. Meinecke, B. Grimm, and C. F. Beck Heme, a Plastid-Derived Regulator of Nuclear Gene Expression in Chlamydomonas PLANT CELL, March 1, 2008; 20(3): 552 - 567. [Abstract] [Full Text] [PDF]

				A. M. Kumar and D. Soll Antisense HEMA1 RNA Expression Inhibits Heme and Chlorophyll Biosynthesis in Arabidopsis Plant Physiology, January 1, 2000; 122(1): 49 - 56. [Abstract] [Full Text] [PDF]