title: Biosynthesis of willardiine and isowillardiine in germinating pea seeds and seedlings.
abstract: The synthesis of the pyrimidinyl amino acids willardiine and isowillardiine was studied in vivo and in vitro. Uracil derivatives stimulate the biosynthesis of both compounds; the free base is the most effective. Significant incorporation of [2-(14)C]uracil and [6-(14)C]orotate into willardiine and isowillardiine was found. Incorporation of [6-(14)C]orotate was substantially decreased in the presence of uracil, and to a lesser extent by uridine and UMP. [3-(14)C]Serine was incorporated into the alanine side chain of the two uracilylalanines but not into the ring. The effect of a number of uracil analogues and inhibitors of pyrimidine metabolism was examined. Some were shown to stimulate the biosynthesis; the most noticeable effects were obtained with 6-azauracil and 2-thiouracil. Attempts to obtain extracts capable of synthesizing the uracilylalanines from uracil and serine were unsuccessful, but weak activity was observed when serine was replaced by O-acetylserine.
mesh_terms: D000409:Alanine / Q000096:biosynthesis* / Q000031:analogs & derivatives; D002247:Carbon Isotopes; D002852:Chromatography, Ion Exchange; D008027:Light; D009963:Orotic Acid / Q000378:metabolism; D011744:Pyrimidinones / Q000096:biosynthesis*; D012639:Seeds / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013889:Thiouracil / Q000494:pharmacology; D014498:Uracil / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology
chemical_list: D002247:Carbon Isotopes; D011744:Pyrimidinones; C002871:isowillardiine; C002872:willardiine; D014498:Uracil; D013889:Thiouracil; D009963:Orotic Acid; D000409:Alanine