Le Pendu J, Cartron J P, Lemieux R U, Oriol R
Institut d'Immuno-Biologie, Hôpital Broussais, Paris, France.
Am J Hum Genet. 1985 Jul;37(4):749-60.
Sera from H normal, secretors and nonsecretors (H/-, Se/- and H/-, se/se), as well as from H-deficient secretors (h/h, Se/- or Bombay secretors) contain enzyme(s) for the transfer of L-fucose in the alpha-configuration to the 2-position of suitable beta-D-galactopyranosyl units. Sera from H-deficient nonsecretors (h/h, se/se; i.e., Bombay nonsecretors) are devoid of such beta-D-Gal alpha-2-L-fucosyltransferase(s). In order to study these enzymes, a comparison was made of the kinetic properties of the enzymes present in the sera of H-normal nonsecretors (H/-, se/se) with those of H-deficient secretors (h/h, Se/se) with those of H-deficient secretors (h/h, Se/-). These studies revealed a clear difference between the two sources of enzyme: (1) the apparent Km for GDP-fucose was four times lower with the H-normal nonsecretor serum (0.008 mM) than with the H-deficient secretor serum (0.028 mM); (2) acceptors with a type 1 or type 3 chain proved to be better than acceptors with a type 2 chain or than phenyl-beta-D-galactopyranoside for the enzyme present in the serum of H-deficient secretor individuals. Indeed, the synthetic type 2 compound, betaDGal (1-->4)-3-deoxy-beta-DGlcNAc-1-OCH3, which cannot act as an acceptor of beta DGlcNAc alpha-3/4-L-fucosyltransferases, remained unchanged in the serum of an H-deficient secretor but was a good acceptor in the serum of an H-normal nonsecretor, and (3) the alpha-2-L fucosyltransferease activity of the H-deficient secretor serum was more sensitive to heat inactivation than that of the H-normal nonsecretor serum (t1/2 at 46 degrees C were 10 min and 75 min, respectively). These results show that at least two distinct alpha-2-L-fucosyltransferases are present in human serum. It is concluded that the enzymatic activity found in the H-deficient secretor serum (h/h, Se/-) could be the product of the Se gene and the enzymatic activity found in the H-normal nonsecretor serum (H/-, se/se) could be the product of the H gene. This conclusion correlates well with the finding that H and Se genes are closely linked and might have derived by gene duplication in the course of evolution.
来自H正常、分泌型和非分泌型个体（H/ - ，Se/ - 和H/ - ，se/se）以及H缺陷分泌型个体（h/h，Se/ - 或孟买分泌型）的血清含有将α构型的L-岩藻糖转移至合适的β-D-吡喃半乳糖基单元2位的酶。来自H缺陷非分泌型个体（h/h，se/se；即孟买非分泌型）的血清缺乏这种β-D-半乳糖α-2-L-岩藻糖基转移酶。为了研究这些酶，对H正常非分泌型个体（H/ - ，se/se）血清中的酶与H缺陷分泌型个体（h/h，Se/se）以及H缺陷分泌型个体（h/h，Se/ - ）血清中的酶的动力学性质进行了比较。这些研究揭示了两种酶来源之间的明显差异：（1）H正常非分泌型血清中GDP-岩藻糖的表观Km（0.008 mM）比H缺陷分泌型血清（0.028 mM）低四倍；（2）对于H缺陷分泌型个体血清中的酶，具有1型或3型链的受体比具有2型链的受体或苯基-β-D-吡喃半乳糖苷更好。实际上，合成的2型化合物β-D-半乳糖（1→4）-3-脱氧-β-D-葡萄糖胺-1-OCH3不能作为β-D-葡萄糖胺α-3/4-L-岩藻糖基转移酶的受体，在H缺陷分泌型个体的血清中保持不变，但在H正常非分泌型个体的血清中是良好的受体，并且（3）H缺陷分泌型血清的α-2-L-岩藻糖基转移酶活性比H正常非分泌型血清对热失活更敏感（46℃时的半衰期分别为10分钟和75分钟）。这些结果表明人血清中至少存在两种不同的α-2-L-岩藻糖基转移酶。得出的结论是，在H缺陷分泌型血清（h/h，Se/ - ）中发现的酶活性可能是Se基因的产物，而在H正常非分泌型血清（H/ - ，se/se）中发现的酶活性可能是H基因的产物。这一结论与H和Se基因紧密连锁且可能在进化过程中通过基因复制产生的发现很好地相关。
