A further study of human seminal plasma lactate dehydrogenase-C4 (LDH-C4): kinetic properties of LDH-C4

Abstract

ヒト乳酸脱水素酵素LDH-C4は硫安塩折, Oxamate-Sepharose 4BおよびAMPのカラムクロマトグラフィーを使用して精製・分離した.この精製・分離したLDH-C4について反応速度を検討した.ヒトLDH-C4はlactateよりα-ketovalerateとpyruvateの方に高い親和性を示した.Km値は各々, pyruvate, α-ketovalerateおよびlactateについて7.7×10-5 M, 1.3×10-3 M, 6.7×10-3 Mであった.ヒトLDH-C4は基質濃度が増加するにつれて酵素活性は抑制され, 特にlactateの場合強く抑制された.ヒト精漿中のLDH-C4と精子中のLDH-C4を比較検討し両者に違いのある可能性を検討した

Lactate dehydrogenase-C4 (LDH-C4) from human seminal plasma was purified by 40-60% (NH4)2SO4 precipitation, Oxamate-Sepharose 4B affinity column chromatography and AMP affinity column chromatography. Enzyme kinetic studies of human seminal plasma LDH-C4 were performed with purified LDH -C4. The human LDH-C4 exhibits a much higher affinity for pyruvate and alpha-ketovalerate than lactate. Apparent Km values for pyruvate, alpha-ketovalerate and lactate were 7.7 X 10(-5) M, 1.3 X 10(-3) M and 6.7 X 10(-3) M, respectively. The human seminal plasma LDH-C4 was severely inhibited by increasing concentration of substrate, especially lactate. These kinetic properties were compared with those of previous reports of human spermatozoa.