1-DEOXY-SPHINGOID BASE AND 1-DEOXYDIHYDROCER BIOSYNTHESIS IN MAMALS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 一种新的狮身人面像碱，1-脱氧鞘氨醇(1-deoxsphinganine)，最近被报道(Zitmer et al.，J.Biol.)化学。284：4786,2009)，在伏马菌素B1(FB1)处理的培养细胞以及暴露于这种真菌毒素的小鼠的肝脏和肾脏中积累。在培养的细胞中，[13C]-L丙氨酸或[13C]棕榈酸酯与[13C]-L丙氨酸或[13C]棕榈酸酯发生缩合反应，生成1-脱氧鞘氨酸。丝氨酸棕榈酰基转移酶(SPT)在缺乏SPT活性(由于LCB1基因突变)的CHO细胞系(LY-B)中缺失，并在野生型LCB1稳定地转回细胞后恢复。这种狮身人面像碱基是由培养细胞和动物(包括人)在正常条件下产生的(即FB1不是其生物合成所必需的)，但被代谢成1-脱氧二氢神经酰胺，而不是累积为游离的狮身人面像碱基。我们确定了SPT利用甘氨酸合成1-脱氧甲基-鞘氨酸胺(1-deoxyl-sphinganine，1-DSA)，并将其代谢为1-脱氧甲基-二氢神经酰胺。相反，没有发现L-苏氨酸被用来制造狮身人面像的碱基类似物。因此，SPT是一种能够利用丝氨酸、丙氨酸或甘氨酸合成三类狮身人面像碱基的三功能酶。此外，这些产物的分布取决于在合成地点可获得的各个前体的相对数量。由于1-脱氧和1-脱氧甲基狮身人面像碱基是由哺乳动物细胞自然产生的，其数量似乎受重要中间代谢产物的平衡控制，因此这些新的脂类似乎在细胞调节中发挥着重要作用。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A novel sphingoid base, 1-deoxysphinganine (1-deoxySa), was recently reported (Zitomer et al., J. Biol. Chem. 284:4786, 2009) to accumulate in fumonisin B1 (FB1) treated cells in culture and in livers and kidneys from mice exposed to this mycotoxin. 1-Deoxysphinganine was shown to arise from condensation of L-alanine with palmitoyl-CoA by following the incorporation of [13C]-L-alanine or [13C]palmitate into [13C]-1-deoxySa by cells in culture. Serine palmitoyltransferase (SPT) was established to be responsible for this reaction because it was absent in a CHO cell line (LY-B) that lacks SPT activity (due to mutation of the LCB1 gene) and restored when wild-type LCB1 was stably transfected back into the cells. This sphingoid base is produced by cells in culture and animals (including humans) under normal conditions (i.e., FB1 is not required for its biosynthesis), but is metabolized to 1-deoxydihydroceramides rather than accumulating as the free sphingoid base. We have determined that glycine is utilized by SPT to synthesize 1-desoxymethyl-sphinganine (1-desoxySa), which is metabolized to 1-desoxymethyl-dihydroceramides. In contrast, L-threonine was not found to be utilized to make a sphingoid base analog. Therefore, SPT is a tri-functional enzyme with the capacity to utilize serine, alanine or glycine to synthesize three categories of sphingoid bases. Furthermore, the distribution of these products is dependent on the relative amounts of the respective precursors available at the site of synthesis. Since 1-deoxy- and 1-desoxymethyl-sphingoid bases are naturally produced by mammalian cells, and the amounts appear to be controlled by the balance of important intermediary metabolites, it seems likely that these novel lipids play significant roles in cell regulation.