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Journal of Lipid Research, Vol. 44, 1737-1743, September 2003
Copyright © 2003 by American Society for Biochemistry and Molecular Biology


* Department of Biochemistry, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo 173-8605, Japan
Department of Pediatrics, University of Tokushima School of Medicine, 3-18-15, Kuramoto-cho, Tokushima 770-8503, Japan
Mitsubishi Kagaku Institute of Life Sciences (MITILS), 11 Minamiooya, Machida, Tokyo 194-8511, Japan
** Neuroscience Center, Departments of Neurology and Psychiatry, University of North Carolina School of Medicine, Chapel Hill, NC 27599
1 To whom correspondence should be addressed. e-mail: ii{at}med.teikyo-u.ac.jp
Sphingolipid activator proteins (saposins A, B, C, and D) are derived from a common precursor protein (prosaposin) and specifically activate in vivo degradation of glycolipids with short carbohydrate chains. A mouse model of prosaposin deficiency (prosaposin-/-) closely mimics the human disease with an elevation of multiple glycolipids. The recently developed saposin A-/- mice showed a chronic form of globoid cell leukodystrophy, establishing the essential in vivo role of saposin A as an activator for galactosylceramidase to degrade galactosylceramide. Seminolipid, the principal glycolipid in spermatozoa, and its precursor/degradative product, galactosylalkylacylglycerol (GalEAG), were analyzed in the testis of the two mouse mutants by electrospray ionization mass spectrometry.
Saposin A-/- mice showed the normal seminolipid level, while that of prosaposin-/- mice was
150% of the normal level at the terminal stage. In contrast, GalEAG increased up to 10 times in saposin A-/- mice, whereas it decreased with age in the wild-type as well as in prosaposin-/- mice. These analytical findings on the two saposin mutants may shed some light on the physiological function of seminolipid and GalEAG.
Supplementary key words spermatogenesis electrospray ionization mass spectrometry tandem mass spectrometry liquid chromatography-mass spectrometry
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