Biophysical characteristics of testicular sphingomyelins with very long chain polyunsaturated fatty acids.

FURLAND, N.; LUQUEZ, J. M.; ANTOLLINI, S.S.; AVELDAÑO, M. I.

Villa Carlos Paz, Córdoba, Argentina

Congreso; 44 Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular; 2008

Sociedad Argentina de Bioquímica y Biología Molecular

BIOPHYSICAL CHARACTERISTICS OF TESTICULAR SPHINGOMYELINS WITH VERY LONG CHAIN POLYUNSATURATED FATTY ACIDS Furland NE,Luquez JM, Antollini SS and Aveldaño MI INIBIBB, CONICET-UNS, 8000 Bahía Blanca, Argentina E-mail: nfurland@criba.edu.ar Very long-chain (C24 to C36) polyunsaturated fatty acids (VLCPUFA) are important constituents of sphingomyelin (SM) of mammalian spermatogenic cells and spermatozoa. The most abundant VLCPUFA in rat testicular SM are 28:4n-6 and 30:5n-6, followed by 32:5n-6. In order to study some of the biophysical properties of these molecular species, liposomes were prepared from three rat testis SM subfractions differing in the fatty acids bound to sphingosine:  I) C16:0-C18:0, II) C22:0-24:0, and III) C28-C32 VLCPUFA. Their thermal behavior was measured by determining the generalized polarization (GP) of the fluorescent probe Laurdan as a function of temperature. Despite the difference of about 6 carbon atoms in their acyl chains, subfractions I and II showed a similar transition temperature (Tt), around 45ºC. In contrast, SM fraction III (on average 7 carbon longer than fraction II) showed a significantly lower Tt, about 25ºC. Thus, the degree of unsaturation in the amide-bound fatty acid of SM overrides the effect of chain length, causing a low GP value in the liposomes. Opposite to the typical ability of most naturally occurring species of SM to form highly-ordered, closely-packed lipid domains, VLCPUFA-rich SMs may form liquid-disordered lipid domains at physiological temperatures in liposomes and perhaps also in bilayers of the specific germ cells and gametes in which they occur.