Lilla Sergio, Mogna Giovanni, Addeo Francesco
Dipartimento di Scienza degli Alimenti, Università degli Studi di Napoli Federico II, Portici, Italy.
J Agric Food Chem. 2005 Jun 29;53(13):5230-8. doi: 10.1021/jf0478051.
Mass spectrometry has been used to map chymosin from a fermentative source. The copresence of the two known genetic variants A (Asp(244)) and B (Gly(244)) was ascertained in bovine chymosin. By contrast, either the A or the B genetic variant occurred in the three commercial samples of recombinant calf chymosin (RCC). Specific biomarker proteins were searched to identify the enzyme source, in both bovine chymosin and RCC samples. Analyzing the derived tryptic peptides, evidence was provided that RCC and bovine chymosin are mainly formed by (1-323), (3-323), and (40p-323) (suffix "p" denotes residues in the pro-segment region of chymosin), whereas the minor components, (4-323), (5-323), and (6-323), were only detected in bovine chymosin. Additionally, the three commercial RCC samples contained the protein species (1-323), (38p-323), (39p-323), and (40p-323) and the shorter form (3-323). Differentiation of the natural and bioengineered enzyme is based upon the detection of these unique minor components by mass spectrometry.
质谱分析法已被用于绘制来自发酵源的凝乳酶图谱。在牛凝乳酶中确定了两种已知基因变体A（天冬氨酸（244））和B（甘氨酸（244））的共存。相比之下，重组小牛凝乳酶（RCC）的三个商业样品中只出现了A或B基因变体。在牛凝乳酶和RCC样品中均搜索了特定的生物标志物蛋白以识别酶源。通过分析所得的胰蛋白酶肽段，有证据表明RCC和牛凝乳酶主要由（1-323）、（3-323）和（40p-323）组成（后缀“p”表示凝乳酶原片段区域中的残基），而次要成分（4-323）、（5-323）和（6-323）仅在牛凝乳酶中检测到。此外，三个商业RCC样品包含蛋白质种类（1-323）、（38p-323）、（39p-323）和（40p-323）以及较短形式（3-323）。天然酶和生物工程酶的区分基于通过质谱法检测这些独特的次要成分。
