Peptides categories

In an attempt to impose some order upon the heterogeneous molecular nature of opioids, it is convenient to subdivide them broadly into five groups, as follows, of which the peptide category has come to the fore only since 1975 ... 

A considerable number of mycotoxins that show high toxicity to vertebrates and/ or invertebrates are produced by organisms associated with crop plants (Flannigan 1991). There are many known cases of human poisoning caused by such compounds. There are three broad categories of mycotoxins represented here, based on the structures of the intermediates from which these secondary metabolites are derived. They are (1) compounds derived from polyketides, (2) terpenes derived from mevalonic acid, and (3) cyclic peptides and derivatives thereof. 

The characteristics and possible mechanisms of action of cytolytic peptides isolated from sea anemones during the past 20 years are described. These agents fall into three categories (1)... 

Because the basic structure of signal peptides is common between bacteria and eukaryotes, all prediction methods can be applied to each category of data although the differences of the optimized, numeric parameters exist. Certainly, a method with high accuracy would be desirable for practical uses. However, it is difficult to compare the perfor-... 

In terms of their chemical structures, signalling molecules fall into five main categories (i) peptides, (ii) steroids, (iii) amino acids and their derivatives, (iv) fatty acid derivatives, and (v) nucleotides. 

Numerous methods have been developed for attaching ligands to the surface of liposomes for reviews, see Refs. (3,6 ). For peptides, they fall into two major categories (i) covalent coupling of the peptides to preformed liposomes that contain functionalized hydrophobic anchors such as, e.g., derivatives of phos-phatidylethanolamine (PE) or (ii) incorporation of lipopeptides, obtained by conjugation of peptides to hydrophobic anchors (fatty acids, phospholipids), into liposomes either during the preparation of the vesicles or by postinsertion into preformed vesicles. In this section, we will briefly discuss these techniques and focus on the ones we have been using in our own work. 

A number of nonprotein amino acids with unsaturated side chains have been isolated. Many of these contain alkene side chains, but some alkyne side chains containing amino acids have also been identified. Nonprotein dehydroamino acids do not have an a-stereocenter these amino acids are still classified under this category. Dehydroamino acids are generally biosynthesized by the enzymatic elimination of a leaving group at the /3-carbon. For example, serine and threonine are enzymatically dehydrated to give dehydroalanine and dehydrobutyrine, respectively. A similar biosynthetic pathway is hypothesized for dehydroamino acids found in nonribosomal peptides, such as nodularins and microcystins. ... 

Describing the whole kingdom of plant defense peptides in depth is beyond the scope of this chapter. In this section a few more peptide toxin activities implied in plant defense will be mentioned that do not fit into the categories mentioned before. 

Included in this category of compounds are one example of a substrate analogue containing an 7V-ketoalkyl scissile bond surrogate moiety (213), and a number of non-substrate analogue peptides Table 8.19) [176, 209-214]. Some of the latter compounds contain a Cys residue whose side-chain may be interacting with the active site Zn(II) atom. All of these compounds are... 

There are many neurotransmitters. The known neurotransmitters (and new ones are occasionally discovered) are a heterogeneous collection of molecules. Most fall into one of three structural categories amino acids, amines, and peptides. Amino acid and... 

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