1. Glycopeptides from human kappa-chains
C P Milstein, C Milstein Biochem J. 1971 Jan;121(2):211-5. doi: 10.1042/bj1210211.
Glycopeptides have been isolated from tryptic digests of kappa-type light chains separated from human myeloma proteins obtained from the serum of two patients, Car and Rai. The glycopeptides are derived from the variable region of the chain in both cases, but from different sections. On the basis of homology it is deduced that glycopeptide from Car, kappaI type, is derived from position 25-31 whereas that from Rai, kappaII type, is from position 62-77, their sequences being respectively Ala-Ser-Gln-Asn-Ile-Ser and Phe-Ser-Gly-Ser-Gly-Ser-Gly(Thr,Asp)Phe-Thr-Leu-Asx-Ile-Ser-Arg. The significance of the results is discussed in connexion with the nature of the attachment site of carbohydrate to protein.
2. Taste and stability characteristics of two key umami peptides from pufferfish (Takifugu obscurus)
Ninglong Zhang, Hai Liu, Xirui Zhou, Wenli Wang, Yuxia Fan, Yuan Liu Food Chem. 2022 Mar 1;371:131124. doi: 10.1016/j.foodchem.2021.131124. Epub 2021 Sep 15.
Takifugu obscurus (T. obscurus) is known for its umami taste. Two taste-active peptides, Pro-Val-Ala-Arg-Met-Cys-Arg (PR-7) and Tyr-Gly-Gly-Thr-Pro-Pro-Phe-Val (YV-8), were proved as key compounds that contributed to the typical taste of T. obscurus. However, whether these peptides have the potential as umami supplements is unknown. The purpose of this study was to investigate the taste characteristics of PR-7 and YV-8, as well as stability at different pH values by sensory evaluation, instrumental analysis and quantum chemical calculation. The results indicated that PR-7 and YV-8 presented umami taste at near neutral pH (6.5-8.0) and had umami-enhancing effects. PR-7 also exhibited significant kokumi activity. Additionally, two peptides showed remarkable stability after different pH treatments, especially YV-8; this may be related to its stable structural property. All the results suggest that both peptides have great potential to be applied in complex foods to provide desirable taste, and act as a feasible alternative to monosodium l-glutamate.
3. A single mRNA encodes multiple copies of the egg peptide speract
C S Ramarao, D J Burks, D L Garbers Biochemistry. 1990 Apr 3;29(13):3383-8. doi: 10.1021/bi00465a034.
A complementary DNA clone (2.3 kb) that encodes the egg peptide speract (Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly) has been isolated from an ovary cDNA library of the sea urchin. Stronglyocentrotus purpuratus. The DNA sequence predicts an open reading frame of 296 amino acids. The likely site of initiation, however, is a downstream in-frame translation initiation codon that would result in a polypeptide of 260 amino acids containing 10 decapeptides, each separated by a single lysine residue. Four of the peptides are speract, and six have the predicted structures of Gly-Phe-Ala-Leu-Gly-Gly-Gly-Gly-Val-Gly (occurs twice), Gly-Phe-Asn-Leu-Asn-Gly-Gly-Gly-Val-Gly, Gly-Phe-Ser-Leu-Thr-Gly-Gly-Gly-Val-Gly, Gly-Thr-Met-Pro-Thr-Gly-Ala-Gly-Val-Asp, and Ile-Asp-His-Asp-Thr-Leu-Ala-Ser-Val-Ser. The isolated cDNA insert hybridized to two species of ovarian mRNA (1.2 and 2.3 kb) obtained from species known to produce speract or speract-like peptides, but failed to hybridize to RNA from other species. Subsequently, a second ovarian cDNA clone (1.2 kb) was isolated and sequenced; this clone contained two additional potential decapeptides: Ser-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly and Ser-Thr-Met-Pro-Thr-Gly-Ala-Gly-Val-Asp. The various speract and speract-like peptides found in egg-conditioned media, therefore, reflect, in part, variable structures within a single copy of mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
