Transketolase (TK), a thiamine diphosphate (ThDP)-dependent enzyme, catalyzes several key reactions of non-oxidative branch of pentose phosphate pathway. TK is a homodimer with two active sites that locate at the interface between the contacting monomers. Both ThDP and bivalent cations are strictly needed for TK activation, just like that for all ThDP-dependent enzymes. TK exists in all organisms that have been investigated. Up to now, one TK gene (TKT) and two transketolase-like genes (TKTL1 and TKTL2) have been identified in human genome. TKTL1 is reported to play a pivotal role in carcinogenesis and may have important implications in the nutrition and future treatment of patients with cancer. Researchers have found TK variants and reduced activities of TK enzyme in patients with neurodegenerative diseases, diabetes, and cancer. Recent studies indicated TK as a novel role in the prevention and therapy of these diseases.
转酮醇酶 (Transketolase, TK) 是一种焦磷酸硫胺素 (thiamine diphosphate, ThDP) 依赖性酶, 负责催化磷酸戊糖通路中碳水化合物转化的一个关键反应。 此酶属于同源二聚体, 在单体间的接触界面上存在两个活性部位。 与所有的焦磷酸硫胺素依赖性酶一样, TK 活性不仅依赖于焦磷酸硫胺素的存在, 还需要二价阳离子。 TK 存在于所有研究过的生物体中。 迄今为止, 在人类基因组中, 已经确定了一个 TK 基因和两个 TK 相似基因, 即转酮醇酶基因 (TKT)、 转酮醇酶样基因-1 (transketolase like-1, TKTL-1) 和转酮醇酶样基因-2 (transketolase like-2, TKTL-2)。 据报道, TKTL-1 在肿瘤发生中起着重要的作用, 同时对肿瘤患者的营养搭配及未来的治疗等方面有着重要的提示。 在神经变性疾病、 糖尿病和癌症中均发现转酮醇酶样基因变异体的存在, 转酮醇酶的活性也有所降低。 这些资料为更好地研究这些疾病的发病机理提供了新的线索, 并有助于建立新的预防和治疗手段。