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Nonenzymatic Spontaneous Oxidative Transformation of 5,6-Dihydroxyindole. Int J Mol Sci 2020; 21:ijms21197321. [PMID: 33023030 PMCID: PMC7583787 DOI: 10.3390/ijms21197321] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 09/26/2020] [Accepted: 10/01/2020] [Indexed: 01/11/2023] Open
Abstract
Melanin is an important phenolic skin pigment found throughout the animal kingdom. Tyrosine and its hydroxylated product dopa provide the starting material for melanin biosynthesis in all animals. Through a set of well-established reactions, they are converted to 5,6-dihydroxyindole (DHI) and DHI-2-carboxylic acid (DHICA). Oxidative polymerization of these two indoles produces the brown to black eumelanin pigment. The steps associated with these transformations are complicated by the extreme instability of the starting materials and the transient and highly reactive nature of the intermediates. We have used mass spectral studies to explore the nonenzymatic mechanism of oxidative transformation of DHI in water. Our results indicate the facile production of not only dimeric and trimeric products but also higher oligomeric forms of DHI upon exposure to air in solution, even under nonenzymatic conditions. Such instantaneous polymerization of DHI avoids toxicity to self-matter and ensures the much-needed deposition of melanin at (a) the wound site and (b) the infection site in arthropods. The rapid deposition of DHI melanin is advantageous for arthropods given their open circulatory system; the process limits blood loss during wounding and prevents the spread of parasites by encapsulating them in melanin, limiting the damage.
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Barek H, Sugumaran M, Ito S, Wakamatsu K. Insect cuticular melanins are distinctly different from those of mammalian epidermal melanins. Pigment Cell Melanoma Res 2017; 31:384-392. [DOI: 10.1111/pcmr.12672] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 11/03/2017] [Indexed: 12/01/2022]
Affiliation(s)
- Hanine Barek
- Department of Biology; University of Massachusetts Boston; Boston MA USA
| | - Manickam Sugumaran
- Department of Biology; University of Massachusetts Boston; Boston MA USA
| | - Shosuke Ito
- School of health Sciences; Fujita Health University; Toyoake Japan
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Whitten MMA, Coates CJ. Re-evaluation of insect melanogenesis research: Views from the dark side. Pigment Cell Melanoma Res 2017; 30:386-401. [PMID: 28378380 DOI: 10.1111/pcmr.12590] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 03/29/2017] [Indexed: 12/16/2022]
Abstract
Melanins (eumelanin and pheomelanin) are synthesized in insects for several purposes including cuticle sclerotization and color patterning, clot formation, organogenesis, and innate immunity. Traditional views of insect immunity detail the storage of pro-phenoloxidases inside specialized blood cells (hemocytes) and their release upon recognition of foreign bodies. Activated phenoloxidases convert monophenols into reactive quinones in a two-step enzymatic reaction, and until recently, the mechanism of tyrosine hydroxylation remained a mystery. Herein, we present our interpretations of these enzyme-substrate complexes. The resultant melanins are deposited onto the surface of microbes to immobilize, agglutinate, and suffocate them. Phenoloxidase activity and melanin production are not limited to the blood (hemolymph) or cuticle, as recent evidence points to more diverse, sophisticated interactions in the gut and with the resident symbionts. This review offers insight into the somewhat neglected areas of insect melanogenesis research, particularly in innate immunity, its role in beneficial insects such as pollinators, the functional versatility of phenoloxidases, and the limitations of common experimental approaches that may impede progress inadvertently.
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Du MH, Yan ZW, Hao YJ, Yan ZT, Si FL, Chen B, Qiao L. Suppression of Laccase 2 severely impairs cuticle tanning and pathogen resistance during the pupal metamorphosis of Anopheles sinensis (Diptera: Culicidae). Parasit Vectors 2017; 10:171. [PMID: 28376914 PMCID: PMC5381134 DOI: 10.1186/s13071-017-2118-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 03/28/2017] [Indexed: 01/15/2023] Open
Abstract
Background Phenol oxidases (POs) catalyze the oxidation of dopa and dopamine to melanin, which is crucial for cuticle formation and innate immune maintenance in insects. Although, Laccase 2, a member of the PO family, has been reported to be a requirement for melanin-mediated cuticle tanning in the development stages of some insects, whether it participates in cuticle construction and other physiological processes during the metamorphosis of mosquito pupae is unclear. Methods The association between the phenotype and the expression profile of Anopheles sinensis Laccase 2 (AsLac2) was assessed from pupation to adult eclosion. Individuals showing an expression deficiency of AsLac2 that was produced by RNAi and their phenotypic defects and physiological characterizations were compared in detail with the controls. Results During the dominant expression period, knockdown of AsLac2 in pupae caused the cuticle to be unpigmented, and produced thin and very soft cuticles, which further impeded the eclosion rate of adults as well as their fitness. Moreover, melanization immune responses in the pupae were sharply decreased, leading to poor resistance to microorganism infection. Both the high conservation among Laccase 2 homologs and a very similar genomic synteny of the neighborhood in Anopheles genus implies a conservative function in the pupal stage. Conclusions To our knowledge, this is the first study to report the serious phenotypic defects in mosquito pupae caused by the dysfunction of Laccase 2. Our findings strongly suggest that Laccase 2 is crucial for Anopheles cuticle construction and melanization immune responses to pathogen infections during pupal metamorphosis. This irreplaceability provides valuable information on the application of Lacccase 2 and/or other key genes in the melanin metabolism pathway for developing mosquito control strategies. Electronic supplementary material The online version of this article (doi:10.1186/s13071-017-2118-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ming-Hui Du
- Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China
| | - Zheng-Wen Yan
- Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China
| | - You-Jin Hao
- Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China
| | - Zhen-Tian Yan
- Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China
| | - Feng-Ling Si
- Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China
| | - Bin Chen
- Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China.
| | - Liang Qiao
- Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China.
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ArgTX-636, a polyamine isolated from spider venom: A novel class of melanogenesis inhibitors. Bioorg Med Chem 2016; 24:5685-5692. [DOI: 10.1016/j.bmc.2016.08.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 08/14/2016] [Accepted: 08/18/2016] [Indexed: 11/19/2022]
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Critical Analysis of the Melanogenic Pathway in Insects and Higher Animals. Int J Mol Sci 2016; 17:ijms17101753. [PMID: 27775611 PMCID: PMC5085778 DOI: 10.3390/ijms17101753] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 10/11/2016] [Accepted: 10/12/2016] [Indexed: 12/24/2022] Open
Abstract
Animals synthesize melanin pigments for the coloration of their skin and use it for their protection from harmful solar radiation. Insects use melanins even more ingeniously than mammals and employ them for exoskeletal pigmentation, cuticular hardening, wound healing and innate immune responses. In this review, we discuss the biochemistry of melanogenesis process occurring in higher animals and insects. A special attention is given to number of aspects that are not previously brought to light: (1) the molecular mechanism of dopachrome conversion that leads to the production of two different dihydroxyindoles; (2) the role of catecholamine derivatives other than dopa in melanin production in animals; (3) the critical parts played by various biosynthetic enzymes associated with insect melanogenesis; and (4) the presence of a number of important gaps in both melanogenic and sclerotinogenic pathways. Additionally, importance of the melanogenic process in insect physiology especially in the sclerotization of their exoskeleton, wound healing reactions and innate immune responses is highlighted. The comparative biochemistry of melanization with sclerotization is also discussed.
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Preparation of melanin from Catharsius molossus L. and preliminary study on its chemical structure. J Biosci Bioeng 2015; 119:446-54. [DOI: 10.1016/j.jbiosc.2014.09.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 08/19/2014] [Accepted: 09/13/2014] [Indexed: 11/23/2022]
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Vavricka CJ, Han Q, Mehere P, Ding H, Christensen BM, Li J. Tyrosine metabolic enzymes from insects and mammals: a comparative perspective. INSECT SCIENCE 2014; 21:13-19. [PMID: 23955993 DOI: 10.1111/1744-7917.12038] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/17/2013] [Indexed: 06/02/2023]
Abstract
Differences in the metabolism of tyrosine between insects and mammals present an interesting example of molecular evolution. Both insects and mammals possess fine-tuned systems of enzymes to meet their specific demands for tyrosine metabolites; however, more homologous enzymes involved in tyrosine metabolism have emerged in many insect species. Without knowledge of modern genomics, one might suppose that mammals, which are generally more complex than insects and require tyrosine as a precursor for important catecholamine neurotransmitters and for melanin, should possess more enzymes to control tyrosine metabolism. Therefore, the question of why insects actually possess more tyrosine metabolic enzymes is quite interesting. It has long been known that insects rely heavily on tyrosine metabolism for cuticle hardening and for innate immune responses, and these evolutionary constraints are likely the key answers to this question. In terms of melanogenesis, mammals also possess a high level of regulation; yet mammalian systems possess more mechanisms for detoxification whereas insects accelerate pathways like melanogenesis and therefore must bear increased oxidative pressure. Our research group has had the opportunity to characterize the structure and function of many key proteins involved in tyrosine metabolism from both insects and mammals. In this mini review we will give a brief overview of our research on tyrosine metabolic enzymes in the scope of an evolutionary perspective of mammals in comparison to insects.
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Affiliation(s)
- Christopher John Vavricka
- Research Network of Immunity and Health (RNIH), Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
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Kohler LJ, Carton Y, Mastore M, Nappi AJ. Parasite suppression of the oxidations of eumelanin precursors in Drosophila melanogaster. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2007; 66:64-75. [PMID: 17879234 DOI: 10.1002/arch.20199] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
In insects, eukaryotic endoparasites encounter a series of innate immune effector responses mediated in large part by circulating blood cells (hemocytes) that rapidly form multilayer capsules around foreign organisms. Critical components of the encapsulation response are chemical and enzyme-catalyzed oxidations involving phenolic and catecholic substrates that lead to synthesis of eumelanin. These responses are initiated immediately upon infection and are very site-specific, provoking no undesirable systemic responses in the host. In this study, we were interested to learn if the principal oxidation pathways leading to the synthesis of eumelanin in larvae of Drosophila melanogaster were targets for inhibition by immune suppressive factors (ISF) derived from a virulent strain of the endoparasitic wasp Leptopilina boulardi. Comparative in vitro assays monitored by sensitive electrochemical detection methods showed that ISF derived from female reproductive tissues significantly diminished the oxidations of the two diphenol eumelanin precursors, dopamine and 5,6-dihydroxyindole (DHI). The oxidations of the monophenol tyrosine, and two other related diphenols, dopa and 5,6-dihydroxyindole-2-carboxylic acid (DHICA), were not significantly inhibited by ISF. The data suggest that melanogenesis represents at least one of the host responses suppressed by L. boulardi ISF, and that the oxidation pathways selectively targeted for inhibition are those synthesizing decarboxylated pigment precursors derived from DHI. These observations, together with previous reports of adverse effects of ISF on the ability of hemocytes to adhere to foreign surfaces, suggest a multifaceted approach by the parasitoid to circumvent the innate immune response of D. melanogaster.
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Affiliation(s)
- Lara J Kohler
- Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison, WI, USA
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Hase S, Wakamatsu K, Fujimoto K, Inaba A, Kobayashi K, Matsumoto M, Hoshi M, Negishi S. Characterization of the pigment produced by the planarian, Dugesia ryukyuensis. ACTA ACUST UNITED AC 2006; 19:248-9. [PMID: 16704460 DOI: 10.1111/j.1600-0749.2006.00306.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Adachi K, Wakamatsu K, Ito S, Miyamoto N, Kokubo T, Nishioka T, Hirata T. An oxygen transporter hemocyanin can act on the late pathway of melanin synthesis. ACTA ACUST UNITED AC 2005; 18:214-9. [PMID: 15892718 DOI: 10.1111/j.1600-0749.2005.00232.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
5,6-Dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) are precursors of eumelanin. The effects of crustacean hemolymph proteins on these eumelanin-related metabolites were investigated. Zymogram analysis indicated that polymers of hemocyanin (Hc) subunits converted DHI into black pigment while no effects were observed using DHICA as a substrate. Spectrum changes for mixtures of purified Hc and DHI showed a profile similar to oxidized DHI by mushroom tyrosinase while Hc had only slight effects on DHICA. Typical inhibitors of tyrosinase and phenoloxidase severely hampered the production of oxidized DHI. Taken together with previous results, these data indicate that Hc plays a crucial role in the conversion of DHI in the hemolymph of crustaceans, which promotes late reactions in the melanin synthetic pathway as well as early reactions (oxidation of tyrosine and DOPA to dopaquinone).
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Affiliation(s)
- Kohsuke Adachi
- Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Japan
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Sugumaran M. Comparative biochemistry of eumelanogenesis and the protective roles of phenoloxidase and melanin in insects. PIGMENT CELL RESEARCH 2002; 15:2-9. [PMID: 11837452 DOI: 10.1034/j.1600-0749.2002.00056.x] [Citation(s) in RCA: 303] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The phenolic biopolymer eumelanin is an important skin pigment found throughout the animal kingdom. The enzyme, tyrosinase, initiates melanogenesis in mammals. The biogenesis is assisted by a number of mammalian protein factors including dopachrome tautomerase and 5,6-dihydroxyindole-2-carboxylate oxidase. Invertebrates, such as insects, employ phenoloxidase and dopachrome (decarboxylating) isomerase for melanin biosynthesis. Recently generated molecular biological and biochemical data indicate that tyrosinase and phenoloxidase are distinctly different enzymes in spite of possessing both monophenol monooxygenase activity as well as o-diphenoloxidase activity. Similarly, insect dopachrome isomerase also differs significantly from its mammalian counterpart in several of its properties including the nature of the enzymatic reaction. In addition, there are considerable differences in the eumelanogenic pathways of these two animal groups that include the utility of substrates, use of dihydroxyindoles and the nature of eumelanin pigment. Thus, the biochemistry and molecular biology of melanogenesis in mammals and insects are significantly different. The advantages of generating different eumelanin pigments and intermediates by the insects are discussed.
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Sugumaran M, Nellaiappan K, Amaratunga C, Cardinale S, Scott T. Insect melanogenesis. III. Metabolon formation in the melanogenic pathway-regulation of phenoloxidase activityy by endogenous dopachrome isomerase (decarboxylating) from Manduca sexta. Arch Biochem Biophys 2000; 378:393-403. [PMID: 10860557 DOI: 10.1006/abbi.2000.1848] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tyrosinase initiates melanogenesis in a variety of organisms. The nature of melanin formed is modified subsequently by dopachrome isomerase and other melanogenic proteins. Earlier, we reported the partial purification of dopachrome isomerase (decarboxylating) from the hemolymph of Manduca sexta and demonstrated the generation of a new quinone methide intermediate during melanogenesis (Sugumaran, M., and Semensi, V. (1991) J. Biol. Chem. 266, 6073-6078). In this paper, we report the purification of this enzyme to homogeneity and a novel inhibition mechanism for regulation of phenoloxidase activity. The activity of phenoloxidase isolated from M. sexta was markedly inhibited by purified dopachrome isomerase. In turn, phenoloxidase also reciprocated by inhibiting the isomerase activity. Preformed dopaminechrome did not serve as the substrate for the isomerase; but dopaminechrome that generated in situ by phenoloxidase was readily converted to melanin pigment by the phenoloxidase/isomerase mixture. Furthermore, the isomerase, which has a molecular weight of about 40,000 in native state, exhibited retardation during affinity electrophoresis on sodium dodeyl sulfate (SDS)-polyacrylamide gel electrophoresis gel copolymerized with tyrosinase and migrated with a molecular weight of 50,000, indicating complex formation with phenoloxidase. Electrophoresis of pupal cuticular extract on polyacrylamide gel, followed by activity staining revealed the presence of a protein band carrying both phenoloxidase and isomerase activity. Accordingly, a high-molecular-weight melanogenic complex was isolated from the pharate cuticle of M. sexta. The complex catalyzed the generation of melanochrome from dopa, while the free phenoloxidase produced only dopachrome from the same substrate. When the complex was treated with trace amounts of SDS, which inhibited the activity of dopachrome isomerase present in the complex, then only the conversion of dopa to dopachrome was observed. These studies confirm the formation of a melanogenic complex between phenoloxidase and dopachrome isomerase. By forming a complex and regulating each other's activity, these two enzymes seem to control the levels of endogenous quinones.
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Affiliation(s)
- M Sugumaran
- Department of Biology, University of Massachusetts at Boston, Harbor Campus, Boston, Massachusetts 02125, USA.
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Sugumaran M, Nellaiappan K. Characterization of a new phenoloxidase inhibitor from the cuticle of Manduca sexta. Biochem Biophys Res Commun 2000; 268:379-83. [PMID: 10679212 DOI: 10.1006/bbrc.2000.2138] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Melanin, the phenolic biopolymer that serves as a skin- and hair pigment-protecting agent against harmful solar radiation and a free radical trap, is biosynthesized in animals mainly by the action of tyrosinase also known as phenoloxidase. Regulation of tyrosinase and hence melanogenesis is vital for all animals. In this report, we present the isolation and characterization of a new, heat-labile glycoprotein inhibitor of phenoloxidase from the larvae of Manduca sexta. The inhibitor was isolated from the live larval cuticle by buffer extraction and purified to homogeneity employing ammonium sulfate precipitation, dialysis, and concanavalin A-Sepharose chromatography. It migrated with a molecular weight of 380,000 on SDS-PAGE gels and inhibited the activity of insect and plant as well as fungal phenoloxidases. Inhibitor formed a tight complex with phenoloxidases, which resisted dissociation even by 1% Triton X-100 or SDS. Selective inhibition of phenoloxidase, while acting on certain but not all different substrates, was observed. The physiological importance of this newly discovered high-molecular-weight phenoloxidase inhibitor is discussed.
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Affiliation(s)
- M Sugumaran
- Department of Biology, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, USA.
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