Catalyzes the transfer of sialic acid from the substrate CMP-N-acetylneuraminate to lactosyl lipids as preferred acceptor substrates in vitro, forming alpha-2,3-linked sialosides. Beta-1,4-linked galactosyl lipids are better substrates than beta-1,3-linked galactosyl lipids. The natural acceptor substrate may be cell surface oligosaccharides in lipooligosaccharide (LOS), whose sialylation has been demonstrated vital for the virulence of P.multocida. Divalent metal cations are not required for the alpha-2,3-sialyltransferase activity. kcat is 12 sec(-1) for the sialylation of Lac-beta-Pro-triazole-C14. kcat is 7.9 sec(-1) for the sialylation of Lac-beta-Pro-2AA. Optimum pH is 6.0. Active in a broad pH range of 4.5-10.0. Low activity is found at pH 10.0 and no significant activity is found at pH 4.0. Has been used successfully in the preparative scale synthesis of sialyllactosyl sphingosine (lyso-GM3), which is an important glycolipid and an intermediate for synthesizing more complex glycolipids such as gangliosides. Belongs to the glycosyltransferase 52 family.