Van Cott K E, Butler S P, Russell C G, Subramanian A, Lubon H, Gwazdauskas F C, Knight J, Drohan W N, Velander W H
Department of Chemical Engineering, Pharmaceutical Engineering Institute, Virginia Tech, Blacksburg 24061, USA.
Genet Anal. 1999 Nov;15(3-5):155-60. doi: 10.1016/s1050-3862(99)00020-0.
The mammary gland of transgenic livestock can be used as a bioreactor for producing complex therapeutic proteins. However, the capacity for making a given post-translational modification upon any given polypeptide is uncertain. For example, the efficiency of gamma-carboxylation of glutamic acid in the amino terminal regions of recombinant human protein C (rhPC) and recombinant human Factor IX (rhFIX) is different at similar expression levels. At an expression level of about 200 microg/ml in the milk of transgenic pigs, rhFIX is highly gamma-carboxylated as indicated by pro-coagulant activity and amino acid sequencing. However, only about 20-35% of rhPC has a native, gamma-carboxyglutamic acid-dependent conformation and anti-coagulant activity. Thus, this work provides an example of apparent differences in substrate specificity between two homologous proteins to the endogenous carboxylase of porcine mammary epithelium which leads to varying degrees of post-translational modification.
转基因家畜的乳腺可作为生产复杂治疗性蛋白质的生物反应器。然而，对任何给定多肽进行特定翻译后修饰的能力是不确定的。例如，在相似表达水平下，重组人蛋白C（rhPC）和重组人凝血因子IX（rhFIX）氨基末端区域谷氨酸的γ-羧化效率不同。在转基因猪乳汁中表达水平约为200微克/毫升时，rhFIX具有高度γ-羧化，这通过促凝血活性和氨基酸测序得以表明。然而，只有约20 - 35%的rhPC具有天然的、γ-羧基谷氨酸依赖的构象和抗凝活性。因此，这项工作提供了一个例子，说明两种同源蛋白质对猪乳腺上皮内源性羧化酶的底物特异性存在明显差异，这导致了不同程度的翻译后修饰。
