赖氨酸丙氨酸、苯乙胺基丙氨酸、碱处理食品蛋白和含硫氨基酸对金属酶的失活作用。

Friedman M, Grosjean O K, Zahnley J C

Adv Exp Med Biol. 1986;199:531-60. doi: 10.1007/978-1-4757-0022-0_31.

Synthetic lysinoalanine (LAL) may be a more effective inhibitor of the zinc-containing enzyme carboxypeptidase A than is ethylenediamine tetraacetic acid (EDTA). The enzyme is also inactivated by alkali-treated, lysinoalanine-containing food proteins such as casein, high-lysine corn protein, lactalbumin, soy protein isolate, and wheat gluten, and by alkali-treated zein, which contains no lysinoalanine. Zinc sulfate regenerates only part of the enzymatic activity after exposure to the treated proteins. The extent of inhibition increases with protein concentration and time of treatment. Any inhibition due to phytate is distinct from that due to the treatment. Phenylethylaminoalanine (PEAA), derived from biogenic phenylethylamine, inhibited enzymatic activity of the metalloenzyme carboxypeptidase A (CPA). The inhibition was maximal at pH 7.0 in the pH range 7 to 8.5. The extent of inhibition increased with time of treatment and PEAA concentration. N-acetyl-PEAA did not inhibit the enzyme, suggesting that the free alpha-NH2 group is required for inhibition. PEAA, LAL, sodium phytate, and cysteine also inactivated the copper enzyme, polyphenol, oxidase (tyrosinase) which plays a major role in enzymatic (oxidative) browning of foods. Analogous comparative studies with LAL, EDTA, and sodium phytate suggest that the potency of PEAA as an inhibitor of CPA is similar to that of sodium phytate, and that of the four compounds tested, PEAA is least effective against tyrosinase. Related studies of the iron and copper containing enzyme cytochrome C oxidase showed that EDTA was not inhibitory, PEAA was slightly inhibitory, and LAL and sodium phytate were stronger inhibitors. Mechanistic explanations are offered to account for some of these observations. The possible relevance of these findings to in vivo protein digestion, enzymatic (oxidative) browning of foods, and the mechanism of the lysinoalanine effect on kidney cells are also discussed.

合成赖氨酸丙氨酸（LAL）可能是一种比乙二胺四乙酸（EDTA）更有效的含锌酶羧肽酶A抑制剂。该酶也会被碱处理过的、含赖氨酸丙氨酸的食物蛋白（如酪蛋白、高赖氨酸玉米蛋白、乳白蛋白、大豆分离蛋白和小麦面筋）以及碱处理过的不含赖氨酸丙氨酸的玉米醇溶蛋白所灭活。接触经处理的蛋白质后，硫酸锌只能使部分酶活性恢复。抑制程度随蛋白质浓度和处理时间的增加而增加。任何由植酸盐引起的抑制作用都与处理引起的抑制作用不同。源自生物源苯乙胺的苯乙氨基丙氨酸（PEAA）抑制金属酶羧肽酶A（CPA）的酶活性。在pH值7至8.5范围内，pH为7.0时抑制作用最大。抑制程度随处理时间和PEAA浓度的增加而增加。N-乙酰-PEAA不抑制该酶，这表明抑制作用需要游离的α-NH2基团。PEAA、LAL、植酸钠和半胱氨酸也会使铜酶多酚氧化酶（酪氨酸酶）失活，该酶在食物的酶促（氧化）褐变中起主要作用。对LAL、EDTA和植酸钠进行的类似比较研究表明，PEAA作为CPA抑制剂的效力与植酸钠相似，在所测试的四种化合物中，PEAA对酪氨酸酶的抑制作用最小。对含铁和铜的细胞色素C氧化酶的相关研究表明，EDTA无抑制作用，PEAA有轻微抑制作用，而LAL和植酸钠是更强的抑制剂。文中提供了一些机理解释来解释其中的一些观察结果。还讨论了这些发现与体内蛋白质消化、食物的酶促（氧化）褐变以及赖氨酸丙氨酸对肾细胞影响机制的可能相关性。