Image Haem B 3D vdW.png thumb right 200px Space filling model of Heme B Image Heme.png thumb right 200px Ball and Stick model of Heme B A heme American English or haem British English is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin . Not all porphyrins contain iron, but a substantial fraction of porphyrin containing metalloprotein s have heme as their prosthetic group these are known as hemoprotein s. Hemes are most commonly recognized in their presence as components of hemoglobin , the red pigment in blood , but they are also components of a number of other hemoproteins. Function Image Succinate Dehygrogenase 1YQ3 Haem group.png thumb right The histidine bound heme group of succinate dehydrogenase , an electron carrier in the mitochondria l electron transfer chain . The large semi transparent sphere indicates the location of the iron ion . From PDB 1YQ3 . Hemoproteins have diverse biological functions including the transportation of diatomic gases, chemical catalysis , diatomic gas detection, and electron transfer. The heme iron serves as a source or sink of electrons during electron transfer or redox chemistry. In peroxidase reactions, the porphyrin molecule also serves as an electron source. In the transportation or detection of diatomic gases, the gas binds to the heme iron. During the detection of diatomic gases, the binding of the gas ligand to the heme iron induces conformational changes in the surrounding protein. It has been speculated that the original evolutionary function of hemoproteins was electron transfer in primitive sulfur based photosynthesis pathways in ancestral cyanobacteria like organisms before the appearance of molecular oxygen. ref cite journal author Hardison, R. title The Evolution of Hemoglobin Studies of a very ancient protein suggest that changes in gene regulation are an important part of the evolutionary story journal American Scientist year 1999 volu ... more details
PBB geneid 5447 Cytochrome P450 reductase EC number 1.6.2.4 also known as NADPH ferrihemoprotein oxidoreductase, NADPH hemoprotein oxidoreductase, NADPH P450 oxidoreductase, P450 reductase, POR , CPR, CYPOR is a membrane bound enzyme required for electron transfer to cytochrome P450 in the microsome of the Eukaryote eukaryotic Cell biology cell from a FAD and Flavin mononucleotide FMN containing enzyme NADPH cytochrome P450 reductase POR EC number 1.6.2.4 . Introduction In Bacillus megaterium and Bacillus subtilis , POR is a C terminal domain of CYP102, a single polypeptide self sufficient soluble P450 system P450 is an N terminal domain . The general scheme of electron flow in the POR P450 system is ul border 0 width 60 cellpadding 3 cellspacing 1 align right NADPH center center bgcolor orange center FAD center center center bgcolor yellow center FMN center center center bgcolor lightblue center P450 center center center O sub 2 sub ul The definitive evidence for the requirement of POR in cytochrome P450 mediated reactions came from the work of Lu, Junk and Coon, ref cite journal author Lu, A.Y.H., Junk, K.W. and Coon, M.J. title Resolution of the cytochrome P 450 containing &omega hydroxylation system of liver microsomes into three components journal J. Biol. Chem. volume 244 issue 13 pages 3714 3721 year 1969 pmid 4389465 ref who dissected the P450 containing mixed function oxidase system into three constituent components POR, cytochrome P450, and lipids. Since all microsomal P450 enzymes require POR for catalysis, it is expected that disruption of POR would have devastating consequences. POR knockout mice are embryonic lethal, ref cite journal author Shen, A.L., O Leary, K.A. and Kasper, C.B. title Association of multiple developmental defects and embryonic lethality with loss of microsomal NADPH cytochrome P450 oxidoreductase journal J. Biol. Chem. volume 277 issue 8 pages 6536 6541 year 2002 pmid 11742006 doi 10.1074 jbc.M111408200 ref probably due to lack of ... more details
heteropolypeptide heteropolymer Hemoglobin, human, adult polymer type heterotetramer, sub 2 sub protein type metalloprotein , globulin function oxygen transport cofactors heme 4 image 1GZX Haemoglobin.png image source Structure of human hemoglobin. The protein s font color red font and font color blue font subunits are in red and blue, and the iron containing heme groups in green. From PDB 1GZX Proteopedia Hemoglobin SubunitCount 3 subunit1 Hb 1 gene1 HBA1 locus1 Chromosome 16 Chr. 16 http www.ncbi.nlm.nih.gov Omim getmap.cgi?chromosome 16p13.3 p13.3 subunit2 Hb 2 gene2 HBA2 locus2 Chromosome 16 Chr. 16 http www.ncbi.nlm.nih.gov Omim getmap.cgi?chromosome 16p13.3 p13.3 subunit3 Hb gene3 HBB locus3 Chromosome 11 Chr. 11 http www.ncbi.nlm.nih.gov Omim getmap.cgi?chromosome 11p15.5 p15.5 Hemoglobin IPAc en icon h i m l o b n American and British English spelling differences Simplification of ae and oe also spelled haemoglobin and abbreviated Hb or Hgb is the iron containing oxygen transport metalloprotein in the red blood cell s of all vertebrate s ref cite book last Maton first Anthea authorlink coauthors Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright title Human Biology and Health publisher Prentice Hall year 1993 location Englewood Cliffs, New Jersey, USA pages url doi isbn 0 13 981176 1 ref with the exception of the fish family Channichthyidae ref cite journal last Sidell first Bruce author link coauthors Kristin O Brien publication date date year 2006 title When bad things happen to good fish the loss of hemoglobin and myglobin expression in Antarctic icefishes periodical The Journal of Experimental Biology series publication place place publisher volume 209 issue Pt 10 pages 1791 1802 page url archiveurl archivedate issn pmid 16651546 pmc doi 10.1242 jeb.02091 ref harv ref as well as the tissues of some invertebrate s. Hemoglobin in the blood carries oxygen from the respiratory orga ... more details
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