4,4-dimethylcholesta-8(9),14,24-trien-3beta-ol is reduced to 4,4-dimethylcholesta-8(9),24-dien-3beta-ol [LBR]

Stable Identifier
Reaction [transition]
Homo sapiens
4,4-dimethylcholesta-8(9),14,24-trien-3beta-ol + NADPH + H+ => 4,4-dimethylcholesta-8(9),24-dien-3beta-ol + NADP+ [LBR]
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4,4-dimethylcholesta-8(9),14,24-trien-3beta-ol and NADPH + H+ react to form 4,4-dimethylcholesta-8(9),24-dien-3beta-ol and NADP+, catalyzed by LBR in the nuclear envelope. LBR protein spans the inner nuclear envelope, has an aminoterminal region with properties of a laminin receptor and a carboxyterminal domain with sequence similarity to sterol delta14-reductases (Holmer et al. 1998). Studies of material from an individual with HEM/Greenberg skeletal dysplasia indicate that LBR catalyzes the sterol delta14-reductase step of cholesterol biosynthesis in vivo. DNA sequencing revealed homozygosity for a mutant LBR allele encoding a truncated protein in the affected individual, and cells from the individual accumulated cholesta-8,14-dien-3beta-ol in culture. Transfection of wild-type LBR into the cultured cells reversed the accumulation of cholesta-8,14-dien-3beta-ol (Waterham et al. 2003). This observation is surprising because a second gene, TM7SF2, encodes an efficient sterol delta14-reductase that is localized to the endoplasmic reticulum whose expression is up-regulated in response to sterol depletion (Bennati et al. 2006). The physiological roles of LBR and TM7SF2 in vivo remain to be determined.

Literature References
PubMed ID Title Journal Year
12618959 Autosomal recessive HEM/Greenberg skeletal dysplasia is caused by 3 beta-hydroxysterol delta 14-reductase deficiency due to mutations in the lamin B receptor gene

Waterham, HR, Koster, J, Mooyer, P, van Noort, G, Kelley, RI, Wilcox, WR, Hennekam, RC, Oosterwijk, JC

Am J Hum Genet 2003
Catalyst Activity

delta14-sterol reductase activity of LBR [nuclear envelope]

Orthologous Events
Cross References
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