Peptides 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. 

Antitumor compounds, among them cyclic peptides, terpenoids, and alkaloids isolated from higher plants 99YZ529. 

Grill, E., Winnacker, E.-L. Zenk, M.H. (1985). Phytochelatins The principal heavy-metal complexing peptides of higher plants. Science, 230, 674-6. 

There are no uncoordinated histidine residues in higher plant plastocyanins. However, some algal plastocyanins, including S. obliquus and A. variabilis have a histidine at position 59, which is of particular interest since this lies within the remote acidic patch region [132]. Differences between the two are that whereas S. obliquus PCu(I) is acidic (charge —9), A. variabilis is basic (charge 1-I-). Also S. obliquus has deletions at 57 and 58 with a consequent tightening of the peptide chain in this locality. Fig. 5. Both these plastocyanins were therefore Ru-modified. 

Matsubayashi, Y., Yang, H., Sakagaini, Y (2001) Peptide signals and their receptors in higher plants. Trends Plant Sci. 6, 573-577. 

The first pyrolysin to be cloned from a higher plant was cucumisin from Cucumis melo, an extracellular protease highly abundant in melon fruit [152], Cucumisin was shown to have a broad substrate specificity in that it cleaves a variety of small peptide substrates and eight peptide bonds within the oxidized insulin B chain [153-155]. A similar, broad... 

SYNGE, RICHARD L. M. (1914-1994). An Irish mathematician and physicist who won the Nobel prize for chemistry in 1952 along with Archer J. P. Martin for their invention of partition chromatography. His research was on llie application of mediods of physical chemistry to isolate and analyze proteins, with special attention to antibiotic peptides and higher plants. He received his doctorate from Cambridge. 

Morita H, Nagashima S, Uchiumi Y, Kuroki O, Takeya K, Itokawa H (1996) Cyclic Peptides from Higher Plants. XXVIII. Antitumor Activity and Hepatic Microsomal Biotransformation of Cyclic Pentapeptides, Astins, from Aster tataricus. Chem Pharm Bull 44 1026... 

Another observation of similar importance is the first isolation of an alkaloid of the peptide type from higher plants. Ergosine (20) (and ergosinine) as well as agroclavine were found in Ipomoea argyrophylla Vatke (21). 

Fig. 2.18 Simplified scheme of the cycle/aUocation of magnesium in a green plant. Mg is involved - inter aha - in making peptide bonds, in tricarboxylate cycle, hydrolysis of molecules and binding of CO (ribulose-bisphosphatecarboxylase/oxidase or PEP carboxylase in plants which also employs Mg or Mtf+ in some plants (Kai et al. 2003)). Reaction steps in which Mg takes part as biocatalyst are marked by broken lines/arrows. Citrate and other intermediates of the tricarboxylate cycle, particularly malate, are employed by higher plants for extraction of essential metals, including Mg, Fe and Mn (thus the closed loop) from soil via and by means of the roots. This closed loop depicts a manner of autocatalysis. Amino acids which are required for protein biosynthesis are produced by reductive amination from tricarboxylate cycle intermediates and other 2-oxoadds which likewise eventually...

The common amino acids used in mammalian protein synthesis belong to the L-enantiomeric series. However, fungi also employ the o-enantiomers in the biosynthesis of some secondary metabolites. These are normally formed from the corresponding L-amino acid. Fungi can also make amino acids with structures that differ from those commonly found in mammalian proteins and in higher plants. These unusual amino acids are utilized for the synthesis of secondary metabolites and some peptides. 

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