Synthesis
Details of heme synthesis can be found in the article on porphyrin.
The enzymatic process that produces heme is properly called porphyrin synthesis, as all the intermediates are tetrapyrroles that are chemically classified as porphyrins. The process is highly conserved across biology. In humans, this pathway serves almost exclusively to form heme. In other species, it also produces similar substances such as cobalamin (vitamin B12).
The pathway is initiated by the synthesis of D-Aminolevulinic acid (dALA or δALA) from the amino acid glycine and succinyl-CoA from the citric acid cycle (Krebs cycle). The rate-limiting enzyme responsible for this reaction, ALA synthase, is negatively regulated by glucose and heme concentration. This mechanism is of therapeutic importance: infusion of heme arginate or hematin and glucose can abort attacks of acute intermittent porphyria in patients with an inborn error of metabolism of this process, by reducing transcription of ALA synthase.
The organs mainly involved in heme synthesis are the liver and the bone marrow, although every cell requires heme to function properly. Heme is seen as an intermediate molecule in catabolism of hemoglobin in the process of bilirubin metabolism.
Read more about this topic: Heme
Famous quotes containing the word synthesis:
“In order to begin an analysis, there must already be a synthesis present in the mind.”
—Johan Huizinga (1872–1945)
“It is in this impossibility of attaining to a synthesis of the inner life and the outward that the inferiority of the biographer to the novelist lies. The biographer quite clearly sees Peel, say, seated on his bench while his opponents overwhelm him with perhaps undeserved censure. He sees him motionless, miserable, his head bent on his breast. He asks himself: “What is he thinking?” and he knows nothing.”
—Andre Maurois (1885–1967)
“The spider-mind acquires a faculty of memory, and, with it, a singular skill of analysis and synthesis, taking apart and putting together in different relations the meshes of its trap. Man had in the beginning no power of analysis or synthesis approaching that of the spider, or even of the honey-bee; but he had acute sensibility to the higher forces.”
—Henry Brooks Adams (1838–1918)