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Before I started editing this pathway, there was a conversion of mevalonate-5-PP into Delta-isopentenyl-5-PP. I've changed the latter into Isopentenyl Pyrophospate (also Delta(3)-isopentenyl-PP). So the 5 has been changed into a 3. This is consistent with the pathway as described on wikipedia (en.wikipedia.org/wiki/Mevalonate_pathway) (although the picture there is talking about isopentenyl-5-PP, in the reactions table further below, the conversion of Mevalonate-5-pyrophosphate to 3-isopentenyl pyrophosphate is described). - Pahles 15:08, 22 May 2008 (UTC)
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Cholesterol to 7 dehydrocholesterol (1)
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Could someone please help me (clinician). Is there a pathway from Cholesterol back to 7 dehydrocholesterol in man? Some lecture books in chemistry seem to suggest so but I can't find this in the literature.
Hi SuEs. Well, the enzyme that performs the forward reaction, DHCR7, is technically capable of preforming the reverse reaction (http://enzyme.expasy.org/EC/1.3.1.21), but not under physiological conditions where [NADPH] out numbers [NADP+] by at least 100:1 (http://www.biochemj.org/content/115/4/609). There is literature on the downregulation of DHCR7 in response to high levels of cholesterol, leading to increased vitamin D production (http://www.jbc.org/content/291/16/8363.full.pdf), but I also can't find anything about biological reactions that convert cholesterol back into 7DHC. AlexanderPico 22:34, 25 May 2017 (UTC)
Fixed IPP reactions (1)
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The paths from IPP (isopentenyl pyrophosphate) to FPP (farnesyl pyrophosphate) were a little bit off. In addition to the isomerization path looping to the left, there was also a direct path depicted. The annotations for FPP and FDPS make it clear that IPP isomerizes to DMPP and then *both* act as reactants in a single reaction to form GPP. Another copy of IPP joins GPP in a second reaction to form FPP. AlexanderPico 01:07, 6 November 2016 (UTC)
