Spielholz C, Schlichter D, Wicks W D
J Cyclic Nucleotide Protein Phosphor Res. 1986;11(5):395-406.
Undegraded tyrosine aminotransferase was purified to near homogeneity from rat liver and was confirmed to be a substrate for the beef heart cyclic AMP dependent protein kinase catalytic subunit. Specific antibody was used to quantitate the amount of phosphate incorporated into the enzyme. Phosphate incorporation was maximal at a catalytic subunit to tyrosine aminotransferase molar ratio of 7:1 using 200 microM ATP for 30 to 60 min at 30 degrees C. Phospho-peptide maps of tyrosine aminotransferase phosphorylated in vitro by the catalytic subunit were compared with those of amino-transferase immunoprecipitated from 32P labeled cells treated with and without 8-Br cAMP. Whereas the phospho-peptide maps of tyrosine aminotransferase isolated from cells treated with and without 8-Br cAMP were identical, differences were observed in the peptide map of tyrosine aminotransferase phosphorylated in vitro and in vivo. These results were taken to indicate that the catalytic subunit is not responsible for tyrosine aminotransferase phosphorylation in vivo.
未降解的酪氨酸转氨酶从大鼠肝脏中纯化至接近均一，并被确认为牛心环磷酸腺苷（cAMP）依赖性蛋白激酶催化亚基的底物。使用特异性抗体来定量掺入该酶中的磷酸量。在30℃下，以7:1的催化亚基与酪氨酸转氨酶摩尔比，使用200微摩尔ATP反应30至60分钟时，磷酸掺入量最大。将催化亚基在体外磷酸化的酪氨酸转氨酶的磷酸肽图谱与从用8-溴-cAMP处理和未处理的32P标记细胞中免疫沉淀的转氨酶的磷酸肽图谱进行比较。尽管从用8-溴-cAMP处理和未处理的细胞中分离出的酪氨酸转氨酶的磷酸肽图谱相同，但在体外和体内磷酸化的酪氨酸转氨酶的肽图谱中观察到差异。这些结果表明催化亚基在体内并非负责酪氨酸转氨酶的磷酸化。
