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| Corrino | |
|---|---|
| Name | Corrino |
| Caption | Generalized corrino scaffold |
| Othernames | Corrinoid core |
Corrino is a class of organometallic macrocyclic frameworks related to the corrin ring system and central to many biologically active cofactors. It forms the core scaffold for vitamin B12‑type cofactors and participates in coordination with metal centers such as cobalt, iron, and nickel in diverse biochemical contexts. Corrino frameworks bridge porphyrin, chlorin, and other tetrapyrrolic systems in structural chemistry, linking themes in bioinorganic chemistry, enzymology, and synthetic macrocycle research.
The corrino scaffold is a contracted tetrapyrrolic macrocycle derived from four pyrrole units linked by three methine bridges and one direct carbon–carbon bond, producing a nonaromatic, slightly folded macrocycle related to porphyrin and chlorin. Systematic IUPAC and trivial names for corrino derivatives often reference parent compounds such as the corrin nucleus of coenzyme B12 or the corrinoid family including cobalamin, methylcobalamin, and adenosylcobalamin. In coordination chemistry, corrino ligands are described by donor atom sets (N4) and axial coordination positions occupied by ligands like cyanide (as in cyanocobalamin), water, thiolate residues from methionine, or organometallic substituents such as 5'-deoxyadenosyl. Nomenclature distinguishes between free base corrinoids, metalated corrinoids, and partially reduced or oxidized derivatives such as corrino(II), corrino(III), and corrino(I) oxidation states invoked in studies of cobalt-centered cofactors.
Corrino is frequently used to denote the core architecture of corrin-derived molecules; corrin itself is the parent macrocycle present in vitamin B12 and related corrinoids. Corrinoids encompass a wide family including cobalamin, hydroxocobalamin, aquacobalamin, and natural analogs such as factor F430 and coenzyme F420-related structures where corrino-like scaffolds adopt alternate substituents. The corrino nucleus differs from porphyrin by lacking one methine bridge, resulting in altered aromaticity and coordination geometry; this structural difference underpins distinct electronic properties exploited in enzymes like methylmalonyl-CoA mutase and methionine synthase. Comparative studies link corrinoids to heme and chlorophyll families through common tetrapyrrole biosynthetic pathways, while phylogenetic surveys map corrinoid diversity across bacteria such as Propionibacterium, Streptomyces, and archaea including Halobacterium.
Corrino-derived cofactors are ubiquitous in prokaryotic metabolism and appear in select eukaryotes through symbiosis or dietary uptake; prominent examples are cobalamin-dependent enzymes like methylmalonyl-CoA mutase and methionine synthase found in Escherichia coli, Salmonella enterica, and Mycobacterium tuberculosis. Corrino cofactors mediate radical-based rearrangements, methyl transfers, and reductive dehalogenation in organisms ranging from Pseudomonas to Dehalococcoides species. Environmental niches such as anaerobic sediments, marine microbial mats, and host-associated microbiomes (e.g., human gut microbiota) concentrate corrinoid producers and consumers; symbioses involving Termitidae termites and ruminants reflect corrino exchange linked to vitamin B12 metabolism. In plants and algae, corrinoids are rare but corrinoid-like molecules occur in secondary metabolism of Streptomyces-derived natural products.
Biosynthesis of corrino scaffolds proceeds via the shared tetrapyrrole precursor uroporphyrinogen III in pathways studied in Salmonella typhimurium, Pseudomonas denitrificans, and Rhodobacter species, diverging into cobalamin-specific enzymes such as CobA, CobB, CobC, and CobN that install cobalt and append nucleotide loops. Two major biosynthetic routes—oxygen‑dependent and oxygen‑independent—have been elucidated, involving enzymes characterized in Bacillus megaterium and Propionibacterium freudenreichii. Degradation pathways include oxidative cleavage by monooxygenases and bacterial corrinoid salvaging systems mediated by transporters like BtuB and enzymes such as CbiZ, with ecological importance in corrinoid recycling among Bacteroides and Clostridium species.
Corrinoids underpin pharmaceutical formulations of vitamin B12 used to treat pernicious anemia and cyanide poisoning, with preparations like hydroxocobalamin and cyanocobalamin employed in clinical settings. Industrial fermentation by organisms such as Pseudomonas denitrificans and Propionibacterium shermanii produces cobalamin at commercial scale for nutraceuticals and food fortification. Corrino-dependent biocatalysts are exploited in bioremediation of chlorinated solvents by Dehalococcoides mccartyi and in synthetic chemistry for site-selective radical transformations, with engineered enzymes from Escherichia coli and Bacillus species enabling sustainable synthesis routes. Metalated corrino analogs are investigated as catalysts in homogeneous catalysis and as contrast agents in magnetic resonance imaging research.
Characterization of corrino and corrinoid compounds employs spectroscopic and chromatographic techniques established in studies of adenosylcobalamin and related cofactors: UV‑visible spectroscopy reveals characteristic Soret-like bands; mass spectrometry (LC‑MS, MALDI‑TOF) permits molecular identification; nuclear magnetic resonance (1H, 13C) elucidates ligand environments; and electron paramagnetic resonance (EPR) detects paramagnetic corrino(II) species. High-performance liquid chromatography (HPLC) coupled to diode-array detectors differentiates corrinoid isoforms in microbial extracts from soil microbiome and marine plankton studies. Advanced methods include X‑ray crystallography for enzyme-bound corrinoids in complexes with methyltransferase and radical SAM proteins, and electrochemical techniques to probe redox states in protein active sites.
Foundational work linking corrin derivatives to physiology emerged from early 20th‑century studies on pernicious anemia leading to the isolation of crystalline vitamin B12 in the 1940s by teams including Dorothy Crowfoot Hodgkin and George R. Minot; subsequent structural elucidation of cobalamin earned recognition related to Nobel Prize-era research. The 1960s–1980s saw expansion of corrinoid enzymology with characterization of methyl transfer and radical rearrangement mechanisms in model organisms such as Salmonella and Propionibacterium. Discovery of the corrinoid-dependent reductive dehalogenases in Dehalococcoides and advances in genetic tools for Escherichia coli and Streptomyces accelerated applied uses in fermentation and bioremediation. Contemporary research integrates structural biology (cryo-EM, X-ray), genomics, and synthetic biology to map corrinoid biosynthetic diversity across microbial dark matter and to engineer corrino-dependent catalysts for green chemistry.
Category:Macrocycles Category:Bioinorganic compounds