Galili U, Swanson K
Department of Laboratory Medicine, University of California, San Francisco 94143.
Proc Natl Acad Sci U S A. 1991 Aug 15;88(16):7401-4. doi: 10.1073/pnas.88.16.7401.
The glycosylation enzyme alpha-1,3-galactosyltransferase (alpha 1,3GT; UDPgalactose:beta-D-galactosyl-1,4-N-acetyl-D-glucosaminide alpha-1,3-galactosyltransferase, EC 2.4.1.151) displays a unique pattern of distribution in mammals. It synthesizes an abundance of Gal(alpha 1-3)Gal(beta 1-4)GlcNAc-R (alpha-galactosyl) epitopes within the Golgi apparatus of cells of nonprimate mammals, prosimians, and New World monkeys (platyrrhines). The catarrhines, which include Old World monkeys, apes, and humans, lack this enzyme activity because of the inactivation of the alpha 1,3GT gene. In contrast, the catarrhines produce large amounts of antibodies, designated anti-Gal, against the alpha-galactosyl epitope. The inactivation of the alpha 1,3GT gene in ancestral catarrhines was probably the result of an intensive evolutionary pressure for alteration in the makeup of cell surface carbohydrates (i.e., suppression of alpha-galactosyl epitope expression) and for the production of the anti-Gal antibody. To determine the period in which the alpha 1,3GT gene was inactivated in ancestral catarrhines, comparative sequencing of a 370-base-pair region of this gene was performed by polymerase chain reactions with DNA of various primates. The data suggest that alpha 1,3GT inactivation occurred rather late in the course of catarrhine evolution (less than 28 million years ago), as separate events in apes and in Old World monkeys, after the two groups diverged from each other.
糖基化酶α-1,3-半乳糖基转移酶（α1,3GT；UDP-半乳糖：β-D-半乳糖基-1,4-N-乙酰-D-葡糖胺α-1,3-半乳糖基转移酶，EC 2.4.1.151）在哺乳动物中呈现出独特的分布模式。它在非灵长类哺乳动物、原猴亚目动物和新大陆猴（阔鼻猴类）细胞的高尔基体中合成大量的Gal(α1-3)Gal(β1-4)GlcNAc-R（α-半乳糖基）表位。包括旧大陆猴、猿和人类在内的狭鼻猴类由于α1,3GT基因的失活而缺乏这种酶活性。相反，狭鼻猴类产生大量针对α-半乳糖基表位的抗体，称为抗Gal抗体。祖先狭鼻猴类中α1,3GT基因的失活可能是细胞表面碳水化合物组成改变（即α-半乳糖基表位表达的抑制）以及抗Gal抗体产生的强烈进化压力的结果。为了确定α1,3GT基因在祖先狭鼻猴类中失活的时期，通过聚合酶链反应对该基因370个碱基对区域进行比较测序，使用了各种灵长类动物的DNA。数据表明，α1,3GT失活发生在狭鼻猴类进化过程中相当晚的时期（不到2800万年前），是猿类和旧大陆猴类在彼此分化后各自发生的独立事件。
