Puzach S S, Ostrovskiĭ Iu M
Biokhimiia. 1980 Dec;45(12):2146-52.
Thiaminase (EC 2.5.1.2) from freshwater bivalve molluscs is a polycosubstrate enzyme, which is resistant to temperatures below 55 degrees. The activation energy of the enzyme with cystein is 15077 cal/mole, with aniline--15948 cal/mole. Thiaminase when injected parenterally to albino mice 2 hrs after injection of [2-14C]thiamine causes an extensive destruction of labelled vitamin b1, which is evidenced from the [14C]thiazole content in urine, liver and kidneys. The total radioactivity and the content of [14C]thiazole in the urine samples collected within 6 hrs after thiamine injection are increased. Cysteine and histidine in combination with thiaminase have no activating effect similar to that observed "in vitro". In the experimental series when non-labelled vitamin B1 from animal tissues (liver, kidney, spleen, muscle) was substituted by the labelled one, the parenterally injected enzyme destroyed up to 30-50% of total thiamine content. Brain and skeletal muscle tissues are more resistant to thiaminase action.
来自淡水双壳贝类软体动物的硫胺酶（EC 2.5.1.2）是一种多底物酶，对55摄氏度以下的温度具有抗性。该酶与半胱氨酸反应的活化能为15077卡/摩尔，与苯胺反应的活化能为15948卡/摩尔。在给白化小鼠注射[2-¹⁴C]硫胺素2小时后经肠胃外注射硫胺酶，会导致标记的维生素B1大量破坏，这可从尿液、肝脏和肾脏中的[¹⁴C]噻唑含量得到证明。在注射硫胺素后6小时内收集的尿液样本中，总放射性和[¹⁴C]噻唑含量均增加。半胱氨酸和组氨酸与硫胺酶结合没有观察到类似“体外”的活化作用。在实验系列中，当用标记的维生素B1替代动物组织（肝脏、肾脏、脾脏、肌肉）中的未标记维生素B1时，经肠胃外注射的酶会破坏高达30%-50%的总硫胺素含量。脑和骨骼肌组织对硫胺酶的作用更具抗性。
