Detection of beta-galactosyl(1 leads to 4)N-acetylglucosaminide alpha(2 leads to 3)-sialyltransferase activity in fetal calf liver and other tissues.

Using a micromethodology based on methylation, the specificity of sialic acid transfer to asialo-alpha 1-acid [3H]-glycoprotein in various tissues was studied. CMP-N-acetylneuraminyl: beta-galactosyl(1 leads to 4)N-acetylglucosaminide alpha(2 leads to 3)-sialytransferase activity (an activity which has not been demonstrated before) was detected in fetal calf liver, embryonic chicken brain, human placenta, and several other tissues. With the exception of the placenta all tissues investigated showed a considerable additional activity of CMP-N-acetylneuraminyl: beta-galactosyl(1 leads to 4)N-acetylglucosaminide alpha (2 leads to 6)-sialytransferase. Rat and porcine liver also contained the latter enzyme, but were essentially devoid of the alpha(2 leads to 3)-sialytransferase. Mixed enzyme experiments indicated that the alpha(2 leads to 3)-sialytransferase activity is due to a separate enzyme, which is clearly distinguishable from the CMP-N-acetylneuraminyl: beta-galactosyl(1 leads to 3)N-acetylgalactosaminide alpha(2 leads to 3)-sialytransferase of porcine liver and submaxillary gland.