Tyramine phenolic group

How the aliphatic monomers are incorporated into the suberin polymer is not known. Presumably, activated co-hydroxy acids and dicarboxylic acids are ester-ified to the hydroxyl groups as found in cutin biosynthesis. The long chain fatty alcohols might be incorporated into suberin via esterification with phenylpro-panoic acids such as ferulic acid, followed by peroxidase-catalyzed polymerization of the phenolic derivative. This suggestion is based on the finding that ferulic acid esters of very long chain fatty alcohols are frequently found in sub-erin-associated waxes. The recently cloned hydroxycinnamoyl-CoA tyramine N-(hydroxycinnamoyl) transferase [77] may produce a tyramide derivative of the phenolic compound that may then be incorporated into the polymer by a peroxidase. The glycerol triester composed of a fatty acid, caffeic acid and a>-hydroxy acid found in the suberin associated wax [40] may also be incorporated into the polymer by a peroxidase. 

Metabolites of biogeiuc amines have also been analyzed by GC-ECD. For the simultaneous analysis of 5-hydroxyindole-3-acetic acid (5-HIAA), homovanillic acid (HVA) and m- and p-hydroxyphenylacetic acid (m-, p-HPAA), (metabolites of 5-HT, DA, and m- and p-tyramine acid respectively) in urine, a simple acidic extraction followed by derivatization with PFPA (derivatizes phenols) and hexafluoroisopropanol (deriva-tizes carboxylic acid groups) has been used (Davis et al., 1982 Baker et al., 1987). 

In Clivia miniata, O-methylnorbelladine (343) carrying 3H labels ortho to the phenolic hydroxy group of the tyramine-derived part and reference labels elsewhere is incorporated into lycorine and clivonine with the loss of both the 3H atoms. To explain this result, which contrasts with the previous one in daffodils (95), feeding experiments with [2/3-3H 5-14C]norpluviine (10) and [2a-3H 5-14C]caranine (2) were devised. The first precursor was isolated from daffodil in separate... 

In the biogenesis of the peptide alkaloids the major point of interest is the way in which the macrocycle is closed. There is as yet no evidence, but one suspects that one of the bonds to the ether oxygen is formed last. Since the precursor of the tyramine unit in these bases is doubtless p-hydroxyphenylalanine, the ring might be closed by conjugate addition of the phenolic hydroxy-group to an unsaturated amide of the lasiodine-A (8) type, or perhaps by conjugate addition of an oxidised p-hydroxyphenylalanine unit to an unsaturated amide (12). The... 

Dns-amides are stable to acid hydrolysis, and fairly stable even to hydrolysis with bases. However, transfer of dansyl groups to other bases occurs in mild alkali this reaction must be borne in mind when hydrolysis is carried out in alkaline media. In Table 1 some data concerning the stability of Dns derivatives to hydrolysis are summarized. Phenolic esters are much less stable than the sulphonamides, therefore it is possible to split off the 0-E)ns from 0,N-bis-Dns-aminophenok with melhanolic KOH 128]. This is of analytical interest because the N-Dns-derivatives of tyramine, synephrine etc. have much higher fluorescence efficiencies than the corresponding 0,N-bis-Dns-deiivatives. The derivatives of imidazoles and esters are unstable, both in acid and alkaline media. Dns-deiivatives of imidazoles, can, however, be selectively cleaved with formic acid [29]. This feature of Dns-imidazole derivatives can be exploited in the deler-mination of histamine and methylhistamines [30]. 

Some Amaryllidaceae plants possess a group of alkaloids containing a Cg— C2-N-C1-C6 unit. In this unit, the C6-C2-N moiety is derived from tyrosine or tyramine, and the C -Ci part is derived from phenylalanine through cinnamic acid, p-coumaric acid, and protocatechualdehyde [1]. Tyramine (C6-C2-N unit) and protocatechualdehyde (C -Ci unit) are then combined and methylated to form O-methylnorbelladine, which is a common biosynthetic precursor of various Amaryllidaceae alkaloids. Through para,ortho -, ortho,para - and para,paw-phenol coupling of norbel-ladine, the lycorine, galanthamine, and crinine type alkaloids are formed, respectively [2]. 

Polymers can also be cross-hnked if the enzyme generates reactive functionalities in the polymer chain (Fig. 6.14). Tyramine, for example, can be incorporated into the polymer (e.g., hyaluronic acid, dextran or alginate) and used to cross-link the material through oxidation of the phenol by HRP in the presence of H2O2 (Jin et al., 2007 Kurisawa et al., 2005 Sakai and Kawakami, 2007). In polypeptides, tyrosinase has also been used to oxidise tyrosine to quinone moieties that are able to react further with the functional groups in the side chains of a number of other amino acids (Chen et al., 2002). 

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