Biochemistry and Molecular Biology of Beta-Glucosidases and Alpha-Hydroxynitrile Lyases Involved in Cyanogenesis

参与氰生成的 β-葡萄糖苷酶和 α-羟基腈裂解酶的生物化学和分子生物学

• 批准号: 9630935
• 负责人: Jonathan Poulton
• 金额: $ 5.5万
• 依托单位: University of Iowa
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-01 至 1998-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9630935&HistoricalAwards=false
• 关键词: Biochemistry; Molecular; Biology; Beta; Glucosidases

9630935 Poulton Rosaceous stone fruits (Prunus spp.) are among many commercially important crops that cause cyanide poisoning in humans and livestock through release of hydrogen cyanide from cyanogenic glycosides by endogenous beta-glucosidases and alpha-hydroxynitrile lyases. Black cherry (P. serotina) seeds are highly cyanogenic because they are a rich source of the cyanogenic diglucoside (R)-amydalin and its catabolic enzymes amygdalin hydrolase (AH), prunasin hydrolase (PH) and (R)-mandelonitrile lyase (MDL). In undamaged seeds, large-scale amygdalin hydrolysis is precluded by tissue level compartmentation, since the two beta-glucosidases are located exclusively in the procambium, whereas amygdalin occurs with MDL within the cotyledonary parenchyma cells. Rapid cyanogenesis ensues when tissue disruption breaches critical permeability barriers, allowing amygdalin access to its catabolic enzymes. The objective of this proposal is to gain a better understanidng of the biochemistry and molecular biology of AH, PH and MDL. The Prunus cyanogenic system is complex in that all three enzymes exist as multiple forms, the exact nature and physiological significance of which require clarification. Whether individual isoforms of each catabolic enzyme carry out defferent functions or exhibit differential expression, either temporally or spatially, remains largely unclear. The proposed studies are designed to lead to an improved understanding of the spatial and temporal regulation of cyanogenesis in plants, thereby contributing toward the long-term goal of reducing the toxicity of cyanogenic plants to animals including man. Furthermore, this research will generate important information about the functioning of beta-glucosidases and FAD-containing alpha-hydroxynitrile lyases, thus facilitating future efforts to engineer the substrate specificities of these enzymes for biotechnological purposes.

9630935 Poulton Rosaceous核果（Prunus spp.）是许多商业上重要的作物之一，其通过内源性β-葡糖苷酶和α-羟基腈裂解酶从生氰糖苷中释放氰化氢而引起人和牲畜的氰化物中毒。 黑樱桃（P. crucina）种子是高度生氰的，因为它们是生氰二葡萄糖苷（R）-苦杏仁苷及其分解代谢酶苦杏仁苷水解酶（AH）、prunasin水解酶（PH）和（R）-扁桃腈裂解酶（MDL）的丰富来源。 在未受损的种子中，大规模的苦杏仁苷水解被组织水平的区室化所阻止，因为两种β-葡糖苷酶仅位于原形成层中，而苦杏仁苷与子叶薄壁细胞内的MDL一起发生。 当组织破裂突破关键的渗透屏障时，快速的氰生成增强，使苦杏仁苷进入其分解代谢酶。 本建议的目的是为了更好地了解AH，PH和MDL的生物化学和分子生物学。 李属植物的生氰系统是复杂的，因为所有三种酶都以多种形式存在，其确切性质和生理意义需要澄清。 每个分解代谢酶的个体亚型是否在时间或空间上执行不同的功能或表现出差异表达，在很大程度上仍然不清楚。 这些研究旨在加深对植物生氰的时空调控的理解，从而有助于实现降低生氰植物对包括人类在内的动物的毒性的长期目标。此外，这项研究将产生有关β-葡萄糖苷酶和含FAD的α-羟基腈裂解酶功能的重要信息，从而促进将来为生物技术目的而设计这些酶的底物特异性的努力。