Abstract
Six naturally occurring and three synthetic molecular species of lactosylceramide (LacCer) were used to examine the molecular species specificity of CMP-N-acetylneuraminate:lactosylceramide alpha 2,3-sialyltransferase in a Golgi-rich fraction of rat liver. The enzyme molecular species specificity was determined either in the presence of nonspecific lipid transfer protein or in the presence of detergents. Assays performed in the presence of transfer protein showed that for those lactosylceramide molecular species with either d18:1 or d18:0 long chain base the enzyme activity decreased linearly as the effective carbon number of the fatty acid increased. An increase in the carbon number of the long chain base decreased the activity of the enzyme twice as much as a corresponding increase in the carbon number of the fatty acid. On the other hand, when the enzyme activity was assayed in the presence of detergents, there was no significant difference in activity among the various molecular species of lactosylceramide based upon the carbon number of the fatty acid or on the presence of a double bond in the long chain base. However, the decrease in enzyme activity with an increase in the carbon number of the long chain base persisted. These results demonstrate that sialyltransferase has binding specificity with respect to the long chain base, but not the fatty acid. The apparent molecular species towards the fatty acid is related to the aqueous solubility of the various LacCer molecular species.
Highlights
Six naturally occurring and three synthetic molecular species of lactosylceramide (Laccer) were used to examine the molecular species specificity of CMP-N-acetylneuraminate:lactosylceramide a2,3-sialyltransferase in a Golgi-rich fraction of rat liver
When sialyltransferase activity was measured in the presence of partially purified nonspecific lipid transfer protein, among those LacCer molecular species with the same long chain base (d18:l) in combination with different fatty acids (16:0, 18:0, 20:0, 22:0, 24:1, or 24:O) the activity decreased linearly as the effective carbon number [12, 27] of the fatty acid increased (Fig. 3A)
The activity of the enzyme towards all the molecular species with either a d18:l or d18:O long chain base was directly proportional to the log of the relative retention time (RRT)' of the molecular species on a C18 reversed-phase column (Fig. 1)
Summary
Six naturally occurring and three synthetic molecular species of lactosylceramide (Laccer) were used to examine the molecular species specificity of CMP-N-acetylneuraminate:lactosylceramide a2,3-sialyltransferase in a Golgi-rich fraction of rat liver. When sialyltransferase activity was measured in the presence of partially purified nonspecific lipid transfer protein, among those LacCer molecular species with the same long chain base (d18:l) in combination with different fatty acids (16:0, 18:0, 20:0, 22:0, 24:1, or 24:O) the activity decreased linearly as the effective carbon number [12, 27] of the fatty acid increased (Fig. 3A).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
