Barramundi (Lates calcarifer) desaturase with Δ6/Δ8 dual activities.

Barramundi is a commercially farmed fish in Australia. To examine the potential for barramundi to metabolise dietary α-linolenic acid (ALA, 18:3 n-3), the existence of barramundi desaturase enzymes was examined. A putative fatty acid Δ6 desaturase was cloned from barramundi liver and expressed in yeast.

Elongase reactions as control points in long-chain polyunsaturated fatty acid synthesis.

Background: Δ6-Desaturase (Fads2) is widely regarded as rate-limiting in the conversion of dietary α-linolenic acid (18:3n-3; ALA) to the long-chain omega-3 polyunsaturated fatty acid docosahexaenoic acid (22:6n-3; DHA). However, increasing dietary ALA or the direct Fads2 product, stearidonic acid (18:4n-3; SDA), increases tissue levels of eicosapentaenoic acid (20:5n-3; EPA) and docosapentaenoic acid (22:5n-3; DPA), but not DHA. These observations suggest that one or more control points must exist beyond ALA metabolism by Fads2.

Fatty acid desaturase 2 promoter mutation is not responsible for Δ6-desaturase deficiency.

Dietary essential polyunsaturated fatty acids (PUFAs) require fatty acid desaturases (FADS) for conversion to long-chain PUFAs (LCPUFAs), which are critical for many aspects of human health. A Δ6-desaturase deficiency in a single patient was attributed to an insertion mutation in the FADS2 promoter. Later population studies have shown this thymidine nucleotide (T) insertion to be a common polymorphism (rs3834458).

Endothelial cell COX-2 expression and activity in hypoxia.

The clinical experience with selective cyclooxygenase (COX)-2 inhibitors reveals there are important protective roles for COX-2 in the cardiovascular system. This study examined the response to hypoxia of endothelial cell eicosanoid synthesis with respect to the role of COX-2 and its molecular regulation in hypoxia. Human umbilical vein endothelial cells (HUVEC) were exposed to hypoxia and the effects on COX-2, prostacyclin (PGI(2)) and thromboxane (TXA(2)) synthesis were examined.

Effects of hypoxia on the expression and activity of cyclooxygenase 2 in fibroblast-like synoviocytes: interactions with monocyte-derived soluble mediators.

Objective: Rheumatoid synovium is characterized by hyperplasia of fibroblast-like (type B) synoviocytes (FLS), infiltration with mononuclear leukocytes, and tissue hypoxia. Although the latter is well documented, it has received little attention in dissection of the biochemical events that mediate the inflammatory lesion in rheumatoid arthritis (RA). Therefore, this study was designed to assess the effect of hypoxia on FLS responses to the monokine interleukin-1beta (IL-1beta) and to monocyte conditioned medium.

Identification of AtNDI1, an internal non-phosphorylating NAD(P)H dehydrogenase in Arabidopsis mitochondria.

Plant mitochondria contain non-phosphorylating NAD(P)H dehydrogenases (DHs) that are not found in animal mitochondria. The physiological function, substrate specificity, and location of enzymes within this family have yet to be conclusively determined. We have linked genome sequence information to protein and biochemical data to identify that At1g07180 (SwissProt Q8GWA1) from the Arabidopsis Genome Initiative database encodes AtNDI1, an internal NAD(P)H DH in Arabidopsis mitochondria.

Effects of hypoxia on monocyte inflammatory mediator production: Dissociation between changes in cyclooxygenase-2 expression and eicosanoid synthesis.

Blood-derived monocytes are found at sites of inflammation as well as in solid tumors and atherosclerotic arteries. They are an abundant source of inflammatory eicosanoids such as prostaglandin E2 (PGE2) and thromboxane A2, which are formed via arachidonic acid (AA) metabolism by cyclooxygenase-1/2 (COX-1/2). In vitro studies of inflammatory mediator production are conducted invariably in room air, which does not reflect the oxygen tensions found in monocyte-containing lesions, which are frequently hypoxic.