Roth S, White D
Proc Natl Acad Sci U S A. 1972 Feb;69(2):485-9. doi: 10.1073/pnas.69.2.485.
Evidence is presented suggesting the presence of galactosyl transferases and galactosyl acceptors on the outer surfaces of intact Balb/c 3T3 cells. In addition, the data indicate that these transferases may only be capable of transferring galactose from uridine diphosphate galactose to galactosyl acceptors on adjacent cells after intercellular contact is made (trans-glycosylation). Intact Balb/c 3T12 cells, by contrast, show no requirement for intercellular contact in order to carry out this reaction suggesting that these cells, which do not exhibit contact inhibition of growth, may be able to transfer galactose to acceptors situated on the same cell as the enzyme (cis-glycosylation). Electrophoretic and radioautographic assays were used to detect surface transferase activities in these two cell lines. Results of experiments on cells from sparse and dense cultures, and under conditions where intercellular contact was regulated, are consistent with the above hypothesis.
有证据表明，完整的Balb/c 3T3细胞外表面存在半乳糖基转移酶和半乳糖基受体。此外，数据表明，这些转移酶可能只有在细胞间接触形成后（转糖基化），才能够将尿苷二磷酸半乳糖中的半乳糖转移至相邻细胞的半乳糖基受体上。相比之下，完整的Balb/c 3T12细胞在进行此反应时不需要细胞间接触，这表明这些不表现出生长接触抑制的细胞可能能够将半乳糖转移至与酶位于同一细胞上的受体（顺糖基化）。采用电泳和放射自显影分析法检测这两种细胞系中的表面转移酶活性。在稀疏和致密培养条件下以及在细胞间接触受到调控的条件下对细胞进行的实验结果与上述假设一致。
