Peptide from protein hydrolysis

Schultz observed (Schultz et al., 1961) that on partial hydrolysis of a commercial preparation of ribonuclease with 0.03 N HCl for times varying up to 48 hr at 105°C, up to 14 out of the 15 bound aspartic residues were liberated. He recommends the method for rapid comparative fingerprinting of the resulting peptides from proteins such as human and animal sera, heme proteins, pepsin, and albumins. 

Part 1 of this chapter is intended to provide background material for the analytical procedures described later in this chapter for amino acids and peptides, but it also provides a broad survey of the topic that can be read in isolation from the analytical context. The derivatisation of amino acids is the basis of many of the sensitive analytical amino-acid assay procedures in current use and this chapter covers the normal profile of reactions of the amino and carboxy groups, knowledge of which is an essential prerequisite for appreciating the analytical context. Reactions of peptides are also covered here (e.g. peptide and protein hydrolysis is covered in Section 4.4.7), though the coverage is restricted in scope because parts of this topic are discussed in Chapter 5, where it is relevant to sequence-determination procedures (see also Barrett, 1985). 

Peptide hydrolases (peptidases or proteases, i.e., enzymes hydrolyzing peptide bonds in peptides and proteins, see Chapt. 2) have received particular attention among hydrolases. As already described in Chapt. 2, peptidases are divided into exopeptidases (EC 3.4.11 -19), which cleave one or a few amino acids from the N- or C-terminus, and endopeptidas-es (proteinases, EC 3.4.21-99), which act internally in polypeptide chains [2], The presentation of enzymatic mechanisms of hydrolysis in the following sections will begin with peptidases and continue with other hydrolases such as esterases. 

Bioactive peptides as products of hydrolysis of diverse marine invertebrate (shellfish, crustacean, rotifer, etc.) proteins are the focus of current research. After much research on these muscles and byproducts, some biologically active peptides were identified and applied to useful compounds for human utilization. This chapter reviews bioactive peptides from marine invertebrates in regarding to their bioactivities. Additionally, specific characteristics of antihypertensive, anti-Alzheimer, antioxidant, antimicrobial peptide enzymatic production, methods to evaluate bioactivity capacity, bioavailability, and safety concerns of peptides are reviewed. 

As antioxidant peptides are rarely present in marine invertebrates, they must be released from the parent protein by hydrolysis with enzymes. Various enzymes have been used to release peptides from muscle proteins. To date, different muscle proteins have been extracted, hydrolysed, and their antioxidant activities studied, which is among all invertebrate muscles the most similar to vertebrate skeletal muscle. Various studies have been conducted to investigate the antioxidant properties of hydrolysates or bioactive peptides from marine invertebrate sources like oysters... 

The lability of peptides and proteins to acidic conditions was first reported in 1920 by Dakin,12031 who found that acid hydrolysis of peptides or proteins that contain consecutive N-alkyl amino acids leads to the formation of piperazine-2,5-diones (DKP) this side reaction lowered their yield during amino acid analysis. For example, the piperazine-2,5-dione c[-Hyp-Pro-] was isolated from the hydrolyzate of gelatine. 

Our example is the sequencing of a peptide (P) derived from partial hydrolysis of a protein which, on complete acid hydrolysis, gave Ala, 3 Gly, Glu, His, 3 Lys, Phe, Tyr, 2 Val, and one molar equivalent of ammonia. 

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