Lentil structure

Structure. Amine oxidase from lentil seeds is a dimeric enzyme with a molecular mass of 140 kD [119]. Each subunit has a length of 569 amino acids and carries two carbohydrate side-chains [119, 120] attached to Asn-234 and Asn-364 [120]. 

Structure of the active center. The active centers of this dimeric enzyme are so well embedded into its protein structure that they are inaccessible to the solvent. The two centers are situated approximately 30 A apart from each other but connected by /3-strands. The active center consists of a type 2 copper center and a cofactor. Sequence comparisons have established that the residues His 8, His 246, and His 357 coordinate the copper ions in both yeast and plants (e.g., lentil seeds) [120,122]. The participating cofactor is typical for amine oxidases, diamine oxidases, and lysyl oxidases but has not yet been found in any other protein - 2,4,5-trihydroxy-phenylalanine quinone [123, 124] (also known as TOPA-quinone, TPQ or 6-hydroxy-DOPA quinone), an internal cofactor which is created by post-translational modification of the tyrosine in position 387 [120]. The consensus sequence of the amino acids neighboring the TOPA cofactor are conserved in all known amine oxidases - Asn-TOPA-Asp/Glu [113,120, 123,125-127]. The positions of the histidine ligands relative to TOPA quinone are conserved in all known amine oxidases as well. The chain lengths of the amine oxidase monomers vary according to the organism of origin 692 residues in yeast [128], 762 in bovine serum amine oxidase [128,129] and 569 in the enzyme from lentil seeds [120,130]. 

Recently, the cofactor peptides have also been isolated from semicarbazide-sensitive amine oxidases purified from bovine and porcine aortas [52], sequenced and confirmed to contain the topa quinone. The same topa quinone consensus sequence was also found in the primary structures of amine oxidases from human kidney [53], human retina [54] and rat colon [55], so called amiloride-binding proteins , and amine oxidase from human placenta [56] that shows 81% identity with bovine plasma amine oxidase [57], bovine lung amine oxidase [58], and amine oxidases from pea and lentil seedlings [59,60], chick pea seedlings [61], and Arabidopsis thaliana [62] obtained by the molecular cloning of respective DNAs. 

Loris, R., Steyaert, J., Maes, D., Lisgarten, J., Pickersgill, R. and Wyns, L. 1993, Crystal structure determination and refinement at 2.3-A resolution of the lentil lectin. Biochemistry 32,8772-8781. 

Following is a structural formula for stachyose, a water-soluble tetrasaccharide component of many plants, including lentils and soybeans. Humans cannot digest stachyose, and its accumulation leads to distension of the gut and flatulence. 

Rafftnose, a galactooligosaccharide, is prevalent in legumes, including lentils, dried beans, and soy. Starch is present in many dietary staples, including potatoes, bread, pasta, and rice. Cellulose, a structural component of cell walls, is the primcay component of celery. Hemicellulose is a structural polysaccharide component in the cell walls of many organisms. 

---