富硒玉米蛋白水解物中硒肽及含硒氨基酸的结构鉴定

Structural Identification of Seleno-peptides and Seleno-amino Acids in Se-enriched Corn Protein Hydrolysates

为了明确硒在玉米蛋白中的赋存形式,采用高效液相色谱-质谱联用法(HPLC-MS/MS),结合质谱数据库比对以及高效液相色谱-等离子体质谱法(HPLC-ICP/MS),对富硒玉米蛋白水解物中硒肽及含硒氨基酸的结构进行鉴定。结果确定了5个小肽,其氨基酸序列分别为:SeMet-MeSeCys-Glu、Met-MeSeCys-Glu、MeSeCys-Glu-Asp、Ile-MeSeCys-Glu、γ-Glu-MeSeCys;确定了4种含硒氨基酸,分别为硒代蛋氨酸(SeMet)、硒代乙硫氨酸(SeEt)、L-硒-甲基硒代半胱氨酸(MeSeCys)、硒代胱氨酸(SeCys2)。借助于标样对含硒氨基酸和二肽进行定量,5个硒肽均含MeSeCys,其中只有一个肽段含SeCys2;但在含硒氨基酸中则是以SeMet含量最高为(586.3±49.5)ng/g,最低的是SeCys2为(102.6±9.0)ng/g。

In order to clarify the combination form of selenium in corn proteins,the structures of seleno-peptides in Se-enriched corn protein hydrolysates were identified by HPLC-MS/MS method coupled with mass spectrum database and seleno-amino acids were identified by HPLC-ICP-MS method.Five seleno-peptides were confirmed as SeMet-MeSeCys-Glu,Met-MeSeCysGlu,MeSeCys-Glu-Asp,Ile-MeSeCys-Glu and γ-Glu-MeSeCys,and four seleno-amino acids were identified as selenomethionine（SeMet）,eleno-Ethionine（SeEt）,Se-methylseleno-L-Cysteine（MeSeCys） and selenocystine（SeCys2）,respectively.Seleno-amino acids and dipeptide were been quantified using standard samples.Selenomethionine（SeMet） revealed the highest content（586.3 ± 49.5） ng/g,and Selenocystine（SeCys2） revealed the low content（102.6 ± 9.0） ng/g.Based on the above results,all five selenopeptides contain MeSeCys,and only one contains SeMet.The major seleno-amino acid was SeMet.