Characterization of a Soluble Phosphatidic Acid Phosphatase in Bitter Melon (Momordica charantia)

Abstract

Momordica charantia is often called bitter melon, bitter gourd or bitter squash because its fruit has a bitter taste. The fruit has been widely used as vegetable and herbal medicine. Alpha-eleostearic acid is the major fatty acid in the seeds, but little is known about its biosynthesis. As an initial step towards understanding the biochemical mechanism of fatty acid accumulation in bitter melon seeds, this study focused on a soluble phosphatidic acid phosphatase (PAP, 3-sn-phosphatidate phosphohydrolase, EC 3.1.3.4) that hydrolyzes the phosphomonoester bond in phosphatidate yielding diacylglycerol and Pi. PAPs are typically categorized into two subfamilies: Mg2+-dependent soluble PAP and Mg2+-independent membrane-associated PAP. We report here the partial purification and characterization of an Mg2+-independent PAP activity from developing cotyledons of bitter melon. PAP protein was partially purified by successive centrifugation and UNOsphere Q and S columns from the soluble extract. PAP activity was optimized at pH 6.5 and 53–60°C and unaffected by up to 0.3 mM MgCl2. The Km and Vmax values for dioleoyl-phosphatidic acid were 595.4 µM and 104.9 ηkat/mg of protein, respectively. PAP activity was inhibited by NaF, Na3VO4, Triton X-100, FeSO4 and CuSO4, but stimulated by MnSO4, ZnSO4 and Co(NO3)2. In-gel activity assay and mass spectrometry showed that PAP activity was copurified with a number of other proteins. This study suggests that PAP protein is probably associated with other proteins in bitter melon seeds and that a new class of PAP exists as a soluble and Mg2+-independent enzyme in plants.

Effect of Cadmium-Tolerant Rhizobacteria on Growth Attributes and Chlorophyll Contents of Bitter Gourd under Cadmium Toxicity

“…It bears yellow female and male flowers. In the Northern Hemisphere, flowering occurs during June–July while fruiting occurs during September–November [ 2 , 3 ]. Bitter melon originated in India and was introduced into China in the 14th century.…”

Bitter melon (Momordica charantia): a natural healthy vegetable

“…[11,47] In BM (bitter melon) two isomers of CLnA (conjugated linolenic acid) are present, which are useful against oxidative stress in diabetes. [70,71] Fructose diet-induced hypoadiponectinemia has been reversed by BM (bitter melon). In improving insulin sensitivity, fructose diet-induced hypoadiponectinemia which is reserved by BM offers a therapeutic advantage to insulin resistance.…”

Effects of wall materials on the physicochemical properties of spray-dried bitter gourd (Momordica charantia L.) powders

“…To improve the health-promoting benefits of bitter gourd and for easy consumption, various bitter gourd products, such as bitter gourd tea 15 , 16 , bitter gourd solid drink 17 , bitter gourd and mulberry leaf biscuits 18 , bitter gourd buckwheat cake 19 , and bitter gourd effervescent tablets 20 , have been continuously developed. However, currently, available bitter gourd products on the market are still not widely accepted by consumers because the bitter taste is still not satisfactorily attenuated or masked 21 – 23 .…”