Hormonal higher plants

Mammals, fungi, and higher plants produce a family of proteolytic enzymes known as aspartic proteases. These enzymes are active at acidic (or sometimes neutral) pH, and each possesses two aspartic acid residues at the active site. Aspartic proteases carry out a variety of functions (Table 16.3), including digestion pepsin and ehymosin), lysosomal protein degradation eathepsin D and E), and regulation of blood pressure renin is an aspartic protease involved in the production of an otensin, a hormone that stimulates smooth muscle contraction and reduces excretion of salts and fluid). The aspartic proteases display a variety of substrate specificities, but normally they are most active in the cleavage of peptide bonds between two hydrophobic amino acid residues. The preferred substrates of pepsin, for example, contain aromatic residues on both sides of the peptide bond to be cleaved. 

Donath J, Boland W (1994) Biosynthesis of acyclic homoterpenes in higher plants parallels steroid hormone metabolism. J Plant Physiol 143 473 78... 

In higher plants aromatic amino acids are required not only for protein synthesis, but as precursors for hormones, and a vast diversity of phenylpropanoid or other secondary metabolites. Thus, the availability of aromatic amino acids in a number of the spatially separate compartments of the plant-cell microenvironment is essential. 

Abscisic acid, one of five known types of plant hormone of general distribution throughout higher plants, is not regarded as a tme terpene because it arises by degradation of a carotenoid.99 99b However, its stmcture (Fig. 22-4) is that of a sesquiterpene. 

ABA formation that cannot be readily conducted with higher plants. Similar studies with the fungus Gibberella fujikuroi, which produces gibberellins, have greatly advanced our knowledge of this group of hormones as reported by Fhinney in this Symposium. 

Hormonal Regulation of Genome Activity in Higher Plants... 

Teissere, M. Penon, P. Van Huystee, R. B. Azou, Y. Richard, J. Hormonal control of transcription in higher plants. Biochem. Biophys. Acta., 1975, 402, 391-402. 

Plant hormones appear to be ubiquitous, that is, they are present in all higher plants (and many are also present in lower plants, and even in fungi and bacteria). This universality of plant hormones is remarkable. 

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