Rohfritsch Philippe F, Joosten John A F, Krzewinski-Recchi Marie-Ange, Harduin-Lepers Anne, Laporte Benoit, Juliant Sylvie, Cerutti Martine, Delannoy Philippe, Vliegenthart Johannes F G, Kamerling Johannis P
Bijvoet Center, Department of Bio-Organic Chemistry, Utrecht University, Padualaan 8, NL-3584 CH Utrecht, The Netherlands.
Biochim Biophys Acta. 2006 Apr;1760(4):685-92. doi: 10.1016/j.bbagen.2005.12.012. Epub 2006 Jan 6.
The acceptor specificities of ST3Gal III, ST3Gal IV, ST6Gal I and ST6Gal II were investigated using a panel of beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-(1-->O)(CH(2))(7)CH(3) analogues. Modifications introduced at either C2, C3, C4, C5, or C6 of terminal D-Gal, as well as N-propionylation instead of N-acetylation of subterminal D-GlcN were tested for their influence on the alpha-2,3- and alpha-2,6-sialyltransferase acceptor activities. Both ST3Gal enzymes displayed the same narrow acceptor specificity, and only accept reduction of the Gal C2 hydroxyl function. The ST6Gal enzymes, however, do not have the same acceptor specificity. ST6Gal II seems less tolerant towards modifications at Gal C3 and C4 than ST6Gal I, and prefers beta-D-GalpNAc-(1-->4)-beta-D-GlcpNAc (LacdiNAc) as an acceptor substrate, as shown by replacing the Gal C2 hydroxyl group with an N-acetyl function. Finally, a particularly striking feature of all tested sialyltransferases is the activating effect of replacing the N-acetyl function of subterminal GlcNAc by an N-propionyl function.
使用一组β-D-半乳糖基-(1→4)-β-D-葡萄糖胺基-(1→2)-α-D-甘露糖基-(1→O)(CH₂)(7)CH₃类似物研究了ST3Gal III、ST3Gal IV、ST6Gal I和ST6Gal II的受体特异性。测试了在末端D-半乳糖的C2、C3、C4、C5或C6处引入的修饰，以及亚末端D-葡萄糖胺的N-丙酰化而非N-乙酰化对α-2,3-和α-2,6-唾液酸转移酶受体活性的影响。两种ST3Gal酶都表现出相同的狭窄受体特异性，并且只接受半乳糖C2羟基功能的还原。然而，ST6Gal酶具有不同的受体特异性。与ST6Gal I相比，ST6Gal II似乎对半乳糖C3和C4处的修饰耐受性更低，并且更喜欢β-D-半乳糖胺基-(1→4)-β-D-葡萄糖胺（乳糖二糖胺）作为受体底物，如用N-乙酰基功能取代半乳糖C2羟基所示。最后，所有测试唾液酸转移酶的一个特别显著的特征是用N-丙酰基功能取代亚末端葡萄糖胺的N-乙酰基功能的激活作用。
