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Desaturases fused to their electron donor
Author(s) -
Sperling Petra,
Heinz Ernst
Publication year - 2001
Publication title -
european journal of lipid science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.614
H-Index - 94
eISSN - 1438-9312
pISSN - 1438-7697
DOI - 10.1002/1438-9312(200103)103:3<158::aid-ejlt158>3.0.co;2-1
Subject(s) - cytochrome b5 , chemistry , electron transport chain , stereochemistry , cytochrome c , heme , cytochrome , cytochrome c1 , fatty acid , biochemistry , enzyme , coenzyme q – cytochrome c reductase , mitochondrion
Fatty acid desaturations in the carboxy‐terminal segment from C1—C10 are catalyzed in many, but not in all cases, by desaturase enzymes which are fused to their electron donor cytochrome b 5 . Several of these enzymes (“front‐end desaturases”) from a wide variety of organisms have been cloned and functionally expressed for proof of regio‐, stereo‐ and chain length‐selectivity. In most cases the actual status of the substrate chain, whether coenzyme A thioester or component of a membrane lipid, is not known. The cytochrome b 5 domain is located N‐terminally, internally or C‐terminally. Compared to the free cytochrome b 5 , the fused domains show a significant reduction of acidic amino acid residues on the surface of the four helices enclosing the heme group. It is discussed how this may contribute to hydrophobic domain pairing required for interdomain electron transport. This is in contrast to the mode of interaction of free cytochrome b 5 with its partners, which is governed by electrostatic charge pairing. A look at crystallized or computer‐simulated models involving fused or free cytochrome b 5 helps to outline the problems encountered by optimizing the docking of partners and the exchange of electrons between domains of different degrees of mobility.