A -Pyrroline-5-carboxylic acid

However, following its formation, the semialdehyde undergoes a spontaneous cyclization and is converted to a A -pyrroline-5-carboxylic acid (P5C), a proline precursor. 

Glutamyl-5-semialdehyde - A -pyrroline-5-carboxylic acid + HjO L-Proline NADCP)" 5-oxidoreductase (E.C. 1.5.1.2)... 

Fig. 3. Proline and arginine synthesis and degradation to show interrelationships between the pathways. The structures are glutamic acid (GLU), ornithine (ORN), citrulline (CIT), arginine (ARG), urea. 2-oxo-5-amino valeric acid (OAV), A -pyrroline-2-carboxylic acid (P2C), proline (PRO), A -pyrroline-5-carboxylic acid (P5C), glutamic semialdehyde (GSA).

Incorporation of D,L-[5- C]A -pyrroline-5-carboxylic acid into Nicotine in Nicotiana rustica... 

Increased blood levels are found in the rare inborn errors, the hyperprolinaemias. The metabolic defect in type I hyper-prolinaemia is an absence of proline oxidase, the first enzyme of the proline degradative pathway. A deficiency of A -pyrroline-5-carboxylic acid dehydrogenase, another enzyme involved in proline degradation, may be responsible for type II hyper-prolinaemia. 

The acetone powder extracts also contained an enzyme that reduced hydroxyglutamic semialdehyde to hydroxyproline, with DPNH serving as the electron donor 177c). It appears that this enzyme is the same as A -pyrroline-5-carboxylic acid reductase 177a-d). 

Mycobactin T (77.7) is the siderochrome of the bacterium that causes human tuberculosis. Eight other mycobactins have been obtained from other species of Mycobacteria a genus to which they are confined. They have only two hydroxamate-groups, but another group is present to aid the three-centre binding of ferric iron as strongly as in other siderochromes (Snow, 1970). Pyrimine (77.5), 5-(2-pyridyl)- A -pyrroline-5-carboxylic acid, was isolated from the bacterium Pseudomonas and, unlike the examples mentioned above, it binds ferrows iron. 

A. Pyrimine (L-5(2-pyridyl)-2-amino-5-ketopentanoic acid l-2(2-pyridyl)-A1-pyrroline-5-carboxylic acid 119)... 

The use of an amine donor, which forms an unstable keto coproduct. For instance, cysteinesulfinic acid was used in transamination to furnish the p-sulfinic acid analog of pyruvate, which spontaneously decomposes into SO2 and pymvate [1732]. In a related fashion, a,co-diamino acids, such as ornithine or leucine yield amino-ketoacids, which (nonenzymatically) cyclize to the corresponding A -pyrroline-5-carboxylate and A -piperidine-2-carboxylate, respectively, as dead-end products [1733, 1734],... 

Fio. 13. Metabolism of proline and hydroxyproline X represents H in proline and OH in hydro roline I, proline or hydroxyproline II, A -pyrroline-5-carboxylic add or A -pyrroliiKe-3-hydro]gr-3-carboxylic acid III, glutamic-y-semialdehyde or ir-hydixHgrglutamic- y-semialdehyde IV, glutamic acid or Y-hydroxyglutamic acid. 

Accumulation of A -pyrroline-5-carboxylate from glutamic acid has been demonstrated in a number of microorganisms 116-119). This conversion has been observed with whole cells, no broken cell preparation has been prepared that can reduce glutamic acid. From the reported results, there is a suggestion that a phosphorylation step may be involved 117-119) as is the case in the conversion of aspartic acid to homoserine. Also, a phosphopyridine nucleotide may serve as the reducing agent 117-119). 

The conversion of ornithine to A -pyrroline -carboxylate is better understood, since the transamination reaction by which this occurs has been studied in some detail with Neurospora 121) and liver extracts 122). The equilibrium of the transaminase reaction with a-ketoglutaric acid as amino group acceptor favors A -pyrroline-5-carboxylate formation about 90% of the ornithine is decomposed. 

The mechanism of acid degradation and humin formation is undoubtedly complex. A A -pyrroline derivative was proposed (Gottschalk, 1960) as an initial cyclization product, and this was later substantiated by identification of 4-hydroxy-5-(l,2,3,4,-tetrahydroxybutyl)-A -pyrroline-2-carboxylic acid (XXVI) (Gielen, 1967a). This compound is... 

Decarboxylation with concomitant dehydrogenation occurred in some cyclic amino acids. For example, (I)-proline was converted into a mixture of 1-pyrroline and its trimer. The methyl ester of (L)-proline was simply dehydrogenated to its /i-imine (69%). With two equivalents of IOB in chloroform (L)-proline was converted directly into 2-pyrrolidinone (70%). This transformation was less efficient for pipecolinic acid and ( )-pyrrolidinone-5-carboxylic acid [48]. 

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