Dear Dr. Nirenberg,
With separate mail I will send you next week new preparations of the commercially available Vibrio cholera-sialidase and different test substances.
At the moment we have two pure sialidases; the one I have already mentioned which hydrolizes both 2 - 6' and 2 - 3' linkages of sialic acid to carbohydrates. And another one from influenza A2 virus which readily splits only 2 - 3' linkages. This is the characteristic feature of myxovirus sialidases.
In all (7) isolated acidic oligosaccharides we find 4 types of bonds through which the sialic acid residues are linked to the carbohydrate:
Type I 2 - 3 linkage to galactose
II 2 - 6 linkage to galactose
III 2 - 6 linkage to hexosamine
IV 2 - 8 linkage from sialic acid to sialic acid
Type I in gangliosides, fetuin (JbC 239 567 1964) and acidic 2-glycoproteins from humans
(BBA 49 250 1961).
Type III in submaxillaris mucin
(BBA 38 513 1960)
Type IV in ganglioside III and IV and colominic acid (polymeric sialic acid) (Biochem. 3 247 1964).
As you can see the sialidase we will send splits all these bonds. Only type IV makes some difficulties because in addition to the 2 - 8 linkage a 1 - 9 labile ester linkage can easily be formed and prevent the enzyme to split the 2 - 8 linkage. In these cases one has to open the labile ester linkage first with n/100 NaOH (few minutes). There are of course other difficulties we are just looking for and I shall tell you later. I came back for some weeks to prepare larger amounts of our ATPase which is active on bilayer. I think I will return in spring and hope to see you then and give a talk.
Thank you very much again for this valuable introduction to the nerve growth factor.
Sincerely yours
(Heinrich Muldner)
Manfred Eigen sends his regards.