Soil peptides

Hydrolysis reactions occur by nucleophilic attack at a carbon single bond, involving either the water molecule directly or the hydronium or hydroxyl ion. The most favorable conditions for hydrolysis, e.g. acidic or alkaline solutions, depend on the nature of the bond which is to be cleaved. Mineral surfaces that have Bronsted acidity have been shown to catalyze hydrolysis reactions. Examples of hydrolysis reactions which may be catalyzed by the surfaces of minerals in soils include peptide bond formation by amino acids which are adsorbed on clay mineral surfaces and the degradation of pesticides (see Chapter 22). 

Since hot add hydrolysis was required to release practically all of the amino adds and amino sugars from the soils, it is likely that the amino adds occur in soils in the form of peptides, polypeptides, and proteins dosely assodated with and protected by SOM and inorganic soil constituents such as clay minerals and hydrous oxides of iron and aluminum. Similarly, amino sugars do not appear to exist in soils as free compounds. 

A comparison of the mean amino acid composition of the soils with those of algae, bacteria, fungi, and yeasts showed the greatest similarity to that of bacteria. [4] This suggests, perhaps not too surprisingly, a major role for microorganisms in the synthesis in the soil of amino acids, peptides and proteins from plant and animal residues, and also explains the relatively uniform amino acid composition in different soils. 

As to the origins of the major N compounds identified, it is possible that at least a portion of some of these compounds are pyrolysis products of amino acids, peptides, proteins, [18] and porphyrins (a component of chlorophyll), [19] or originate from the microbial decomposition of plant lignins and other phenolics in the presence of ammonia. [20] Of considerable interest are the identifications aromatic and aliphatic nitriles. Nitriles can be formed from amines with the loss of 2 H2, from amides with the loss of H20, and also by reacting n-alkanoic acid with NH3. [21] The detection of long-chain alkyl- and dialkyl-nitriles points to the presence in the soil or SOM of long-chain amines... 

In contrast to the finding by 1SN NMR that 85 % of the total soil N occurs in proteins or peptides, chemical methods show that only about 40 % of the total soil N occurs in proteins. [4] What are the reasons for these wide divergencies To provide answers to these questions, it may be useful to consider the following ... 

From the data presented herein and in earlier publications, [16,17, 28] it is possible to deduce the following distribution of total N in soils proteinaceous materials (proteins, peptides, and amino acids) 40%, amino sugars 5%, heterocyclic N compounds (including purines and pyrimidines) 35 %, and NH3 20% with about 1/4 of the NH3 fixed as NH4 to clay minerals. Thus, proteinaceous materials and heterocyclic N compounds are the major soil N components. 

Si structure 251 smallpox 70 soil nitrogen compounds detected by 15N NMR, amides/peptides 126 amino adds 126 difficulties encountered with the method 126-127... 

Biological. Four Pseudomonas sp., including Pseudomonas putida (ATCC culture 29607) isolated from soil, degraded chloropicrin by sequential reductive dechlorination. The proposed degradative pathway is chloropicrin -> nitrodichloromethane nitrochloromethane nitromethane + small amounts of carbon dioxide. In addition, a highly water soluble substance tentatively identified as a peptide was produced by a nonenzymatic mechanism (Castro et al., 1983). 

Soil-borne bacteria of the family Rhizobiaceae and leguminous plants form a symbiotic relationship during which a new organ, the root nodule, is developed. Within these root nodules the bacteria fix atmospheric dinitrogen and the product of nitrogen fixation, ammonia, is exported to the plant [69,70]. Root nodules develop from primordia which are established at specific sites in the root cortex shortly after Rhizobium infection. The peptide enod40 is believed to play a critical role in inducing the de-differentiation and the mitotic division of root cortical cells, i.e. the initial steps in nodule development. This however, is not entirely undisputed [3,4,69-72]. 

---