摘要
选用甘氨酸(Gly)、丙氨酸(Ala)、缬氨酸(Val)、亮氨酸(Leu)、异亮氨酸(Ile)、脯氨酸(Pro)、苯丙氨酸(Phe)、色氨酸(Trp)、丝氨酸(Ser)、苏氨酸(Thr)、半胱氨酸(Cys)、谷氨酰胺(Gln)、天冬酰胺(Asn)、谷氨酸(Glu)、天冬氨酸(Asp)、组氨酸(His)、赖氨酸(Lys)及精氨酸(Arg)等18种氨基酸为效应物,研究它们对凡纳滨对虾(Litopenaeusvannamei)N-乙酰-β-D-氨基葡萄糖苷酶催化pNP-NAG水解反应的影响。结果表明,非极性氨基酸及不带电荷的极性氨基酸对NAGase没有明显的抑制作用;带正电荷的碱性氨基酸L-His及Lys有轻微的激活作用,而Arg则先激活后抑制;带负电荷的酸性氨基酸Asp及Glu有明显的抑制作用,其IC50分别为20,28mmol/L。研究Asp,Glu对酶催化pNP-NAG水解反应的抑制作用机理,并测定其抑制常数。研究表明Asp及Glu的抑制作用均表现为可逆效应,抑制类型均为竞争性抑制,其抑制常数KI值分别为9.50mmol/L和11.06mmol/L。
The β-N-Acetyl-D-glucosaminidase （NAGase, EC.3.2.1.52） catalyzes the cleavage of N-acetylglucosamine polymers. It is a composition of the chitinases and cooperates with endo-chitinase and exo-chitinase to disintegrate chitin into N-acetylglucosamine. It is widely distributed in animal tissues and in microorganisms. The effects of some amino acids on the activity of NAGase from the viscera of prawn （Litopenaeus vannamei） were studied. The results showed hydrophobic amino acids and neutral hydrophilic amino acids had no effects on the enzyme activity apparently. The alkaline amino acids activated the enzyme activity lightly, and the order of activation was His 〉 Lys 〉 Arg. The acidic amino acids had inhibitory effects on the enzyme activity, and the inhibitory effects were reversible with remaining enzyme activity. The IC50s of Asp and Glu （the inhibitor concentrations leading to 50% activity loss） were estimated to be 20 and 28 mmol/L, respectively. The inhibitory mechanisms were competitive types and their K1 s were determined to be 9.50 and 11.06 mmol/L respectively.
出处
《海洋科学》
CAS
CSCD
北大核心
2006年第3期46-50,共5页
Marine Sciences
基金
福建省青年科技人才创新项目(2004J054)
福建省教育厅科技计划项目(JA04260)
