GDP

GDP (guanosine diphosphate): see guanine.

Total market value of the goods and services produced by a nation's economy during a specific period of time. GDP is customarily reported on an annual basis. It is defined to include all final goods and services—that is, those that are produced by the economic resources located in that nation regardless of their ownership and are not resold in any form. GDP differs from gross national product (GNP), which is defined to include all final goods and services produced by resources owned by that nation's residents, whether located in the nation or elsewhere.

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GDP-fucose protein O-fucosyltransferase 1 (POFUT1) is an enzyme responsible for adding fucose sugars in O linkage to serine or threonine residues between the second and third conserved cysteines in EGF-like repeats on the Notch protein. The protein is an inverting glycosyltransferase, which means that the enzyme uses GDP-β-L-fucose as a donor substrate and transfers the fucose in O linkage to the protein producing fucose-α-O-serine/threonine.

When the gene for POFUT1 is knocked out, or the expression is decreased to very low levels, all Notch signaling is destroyed, which means that fucose on Notch is absolutely essential for Notch function. Why this is the case is not yet well understood.

Almost all glycosyltransferases reside in the Golgi apparatus. However, POFUT1 as well as the related enzyme POFUT2 have recently been shown to reside in the endoplasmic reticulum.

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