• 作者： 蕭百和; 蘇仲卿; 宋賢一
• 作者服務機構： 國立臺灣大學農業化學系
• 中文摘要： 蘆筍芽中含有豐富的UDPG焦磷解?、經酵素純化方法：Protamine sulfate處理、硫酸銨劃分沈澱、Sephadex
  G-100 膠體過濾，DEAE-cellulose色層分析及磷酸鈣膠色層分析等步驟處理後，可得到純化30倍的焦磷解?。
  蘆筍UDPG焦磷解?在4?以及pH6.0至9.5間較為穩定，其最適pH為7-8。酵素對UTP有絕對特異性，且絕對需要二
  價金屬離子，其中鎂最合適而錳及鈷也有作用，以膠體過濾及蔗糖密度斜坡超離心法，測定酵素分子量約為四萬。在pH
  7.2，UDPG合成方向的表面平衡常數為0.32。
  由產物阻害作用及初速率動力學之研究，可知UDPG焦磷解?之作用機構為次序性雙基質機構，以MgUTP或UDPG
  作為先行基質。MgUTP複合體為酵素的真實基質而UTP競爭性的阻害MgUTP。MgUTP和GIP的Michaelis常數與UDPG
  ，PPi和自由UTP的抑制常數也被測定。
  l
• 英文摘要： UDPG pyrophosphorylase, abundant in asparagus spears, was purified 30-fold from white asparagusspears through procedures of protamine sulfate treatment, ammonium sulfate fractionation, Sephadex G-100gel filtration, DEAE-cellulose ion exchange column chromatography, and calcium phosphate gel-celluloseadsorption column chromatography. Partially purified UDFG pyrophosphorylase was very stable at 4℃ and at pH values between 6.0-9.5.The optimum pH of this enzyme for catalyzlng the reaction in the direction of UDPG synthesis was about7.0-8.0. The enzyme was highly specific for UTP. The divalent cation requirement was most readily satisfiedby magnesium ion, but manganese ion and cobalt ion were also effective. The molecular weight determinedby gel filtration technique and ultracentrifugation was about 40,000. The apparent equilibrium constant atpH 7.2 estimated in the direction of UDPG synthesis was 0.32. From the product in hibition patterns and initial velovity studies, an ordered Bi-Bi reaction mechanismwas indicated in which the nucleotide substrate is added first and released last as the product. MgUTP was the true substrate for the enzyme and free UTP was a competitive inhibitor toward MgUTP . Mi-chaelis constants for UTP and GIP and inhibition constants for UDPG, PPi and free UTP combining withfree enzyme were also determined.
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