Hagen F K, Gregoire C A, Tabak L A
Department of Dental Research and Biochemistry, University of Rochester, New York 14642, USA.
Glycoconj J. 1995 Dec;12(6):901-9. doi: 10.1007/BF00731252.
A UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase (polypeptide GalNAc transferase) cDNA was amplified from rat sublingual, submandibular and parotid glands, brain, skeletal muscle, and liver, using the polymerase chain reaction (PCR) and sequences derived from bovine polypeptide GalNAc transferase-Type 1 (polypeptide GalNAc transferase-T1). The transcripts encoding the rat sublingual gland and bovine enzymes were 91% identical in nucleotide sequence, except in their 5' and 3' untranslated regions. The enzymes encoded by the rat and bovine cDNAs were 559 amino acids in length and were virtually identical (98% amino acid sequence identity and 99.5% homologous overall). Northern blot analysis indicates that the polypeptide GalNAc transferase-T1 transcripts are expressed in many tissues but at widely differing levels. Although the amino acid sequence of polypeptide GalNAc transferase-T1 is conserved among mammals, the pattern of tissue expression varies between rats and humans. For example, the steady-state level of polypeptide GalNAc transferase-T1 transcript is quite low in lung relative to other rat tissues, whereas high expression of this transcript is detected in human lung. Therefore, we surmise that isoforms of polypeptide GalNAc transferase must exist and that isoforms are expressed in a tissue-dependent fashion. Searches of the GenBank database have revealed homologous sequences for several isoforms derived from several human tissues. In addition, hypothetical proteins from C. elegans also display strong homology; evidence suggests six ancestral isoforms of polypeptide GalNAc transferases may exist in C. elegans.
利用聚合酶链反应（PCR）以及源自牛N-乙酰半乳糖胺基转移酶-1（多肽GalNAc转移酶-T1）的序列，从大鼠舌下腺、颌下腺、腮腺、脑、骨骼肌和肝脏中扩增出UDP-N-乙酰半乳糖胺：多肽N-乙酰半乳糖胺基转移酶（多肽GalNAc转移酶）的cDNA。编码大鼠舌下腺和牛该酶的转录本在核苷酸序列上有91%的同一性，但其5'和3'非翻译区除外。大鼠和牛cDNA编码的酶长度均为559个氨基酸，且几乎完全相同（氨基酸序列同一性为98%，总体同源性为99.5%）。Northern印迹分析表明，多肽GalNAc转移酶-T1转录本在许多组织中都有表达，但表达水平差异很大。尽管多肽GalNAc转移酶-T1的氨基酸序列在哺乳动物中是保守的，但大鼠和人类之间的组织表达模式有所不同。例如，相对于大鼠的其他组织，多肽GalNAc转移酶-T1转录本在肺中的稳态水平相当低，而在人肺中则检测到该转录本的高表达。因此，我们推测多肽GalNAc转移酶必定存在同工型，且同工型以组织依赖性方式表达。对GenBank数据库的搜索揭示了源自几种人类组织的几种同工型的同源序列。此外，秀丽隐杆线虫的假设蛋白也显示出很强的同源性；有证据表明秀丽隐杆线虫中可能存在六种多肽GalNAc转移酶的祖先同工型。
