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Studies on bound trans-4-hydroxy-L-proline in sandal (Santalum album L.).

ABSTRACT: 1. trans-4-Hydroxy-l-proline was found to occur in the bound state in the leaves of sandal (Santalum album L.), in which large amounts of free cis-4-hydroxy-l-proline are also present. 2. Bound trans-4-hydroxy-l-proline was present, associated mainly with a ;wall' fraction and a ;soluble' fraction roughly in equal proportions. 3. Bound proline is present only in small amounts in the ;soluble' fraction but is mostly associated with the ;wall' fraction and the other sedimented fractions. 4. In the free amino acid fraction more than 98% of the hydroxyproline had the cis-configuration, whereas in the ;wall' and ;soluble' fractions more than 90% of the bound hydroxyproline was in the trans-configuration. 5. Various extraction procedures indicated heterogeneity of the hydroxyproline-containing components. Hot 5% (w/v) trichloroacetic acid extracts about 25% of hydroxyproline and m-NaOH extracts an additional 25%. 6. Incorporation of [(14)C]proline into the bound hydroxyproline was demonstrated. The hydroxyproline component of the ;soluble' fraction does not appear to be the precursor of that of the ;wall' fraction.

SUBMITTER: Kuttan R

PROVIDER: S-EPMC1179450 | biostudies-other | 1970 Oct

REPOSITORIES: biostudies-other

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Project description:Hydroxyprolines, such as trans-4-hydroxy-l-proline (T4LHyp), trans-3-hydroxy-l-proline (T3LHyp), and cis-3-hydroxy-l-proline (C3LHyp), are present in some proteins including collagen, plant cell wall, and several peptide antibiotics. In bacteria, genes involved in the degradation of hydroxyproline are often clustered on the genome (l-Hyp gene cluster). We recently reported that an aconitase X (AcnX)-like hypI gene from an l-Hyp gene cluster functions as a monomeric C3LHyp dehydratase (AcnXType I). However, the physiological role of C3LHyp dehydratase remained unclear. We here demonstrate that Azospirillum brasilense NBRC 102289, an aerobic nitrogen-fixing bacterium, robustly grows using not only T4LHyp and T3LHyp but also C3LHyp as the sole carbon source. The small and large subunits of the hypI gene (hypIS and hypIL, respectively) from A. brasilense NBRC 102289 are located separately from the l-Hyp gene cluster and encode a C3LHyp dehydratase with a novel heterodimeric structure (AcnXType IIa). A strain disrupted in the hypIS gene did not grow on C3LHyp, suggesting its involvement in C3LHyp metabolism. Furthermore, C3LHyp induced transcription of not only the hypI genes but also the hypK gene encoding Δ1-pyrroline-2-carboxylate reductase, which is involved in T3LHyp, d-proline, and d-lysine metabolism. On the other hand, the l-Hyp gene cluster of some other bacteria contained not only the AcnXType IIa gene but also two putative proline racemase-like genes (hypA1 and hypA2). Despite having the same active sites (a pair of Cys/Cys) as hydroxyproline 2-epimerase, which is involved in the metabolism of T4LHyp, the dominant reaction by HypA2 was clearly the dehydration of T3LHyp, a novel type of T3LHyp dehydratase that differed from the known enzyme (Cys/Thr).IMPORTANCE More than 50 years after the discovery of trans-4-hydroxy-l-proline (generally called l-hydroxyproline) degradation in aerobic bacteria, its genetic and molecular information has only recently been elucidated. l-Hydroxyproline metabolic genes are often clustered on bacterial genomes. These loci frequently contain a hypothetical gene(s), whose novel enzyme functions are related to the metabolism of trans-3-hydroxyl-proline and/or cis-3-hydroxyl-proline, a relatively rare l-hydroxyproline in nature. Several l-hydroxyproline metabolic enzymes show no sequential similarities, suggesting their emergence by convergent evolution. Furthermore, transcriptional regulation by trans-4-hydroxy-l-proline, trans-3-hydroxy-l-proline, and/or cis-3-hydroxy-l-proline significantly differs between bacteria. The results of the present study show that several l-hydroxyprolines are available for bacteria as carbon and energy sources and may contribute to the discovery of potential metabolic pathways of another hydroxyproline(s).

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Studies on bound trans-4-hydroxy-L-proline in sandal (Santalum album L.).

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