Antigen modifications synthesis

One fascinating observation is that PCNA (proliferating cell nuclear antigen) can be modified by multiple forms of ubiquitin, demonstrating that DUBs with different specificities can act at the same location on a specific substrate. PCNA can be modified by mono-ubiquitin, 63-linked polyubiquitin, or SUMO at K164 [89]. Modification of PCNA by mono- or polyubiquitin determines whether it is utilized in translesion synthesis or error-free DNA repair, respectively. SUMO modification prevents PCNA function in DNA repair and instead promotes DNA replication. It is probable that multiple DUBs, as yet unidentified, are required to regulate PCNA modification. 

A large-scale enzymic synthesis of the trisaccharide a-D-Neu5Ac-(2—>3)-j8-D-Gal-( 1 — 3)-d-G1cNAc (65), the tumor-associated carbohydrate antigen CA 50, has been achieved.113 This is a further illustration of the cross reactivity and efficiency of STB, This sialyltransferase, like STA, was partially purified from porcine liver, according to a modification of Conradt s procedure. 114 The initial rate measured for j8-d-Gal-( 1 - 3)-d-G1cNAc at saturating concentration was 18% of the one measured for the real substrate / -d-... 

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