Chlamydomonas reinhardtii에 N-methyl-N-nitroso-N-nitrosoguanidine을 처리하여 acetate 요구성 변이주, KX8215와 KX8261을 얻었고 여기에서 ribulose-1, 5-bisphosphate carboxylase를 분리하여 그 특성을 연구하였다. 2가 금속이온 $Mg^{2+}$, $Ni^{2+}$, $Co^{2+}$ 등은 효소 활성을 증가시켰고 할로겐족 음이온 $Cl^-$, $I^-$, $Br^-$ 등은 효소 활성을 저해하였으나 $Cu^{2+}$는 활성에 거의 영향을 주지 않았다. 또한 변이주 효소의 이온 영향, 최적 pH 그리고 효소 단백질의 함량 등은 야생종의 경우와 별 차이가 없었다. 변이주 효소의 최적온도는 $35^{circ}C$로 야생종 효소의 $25^{circ}C$ 보다 $10^{circ}C$높았다. 중요한 점은 변이주 효소의 고유 활성도가 야생종 효소보다 현저하게 낮아진데 반해 변이주 효소의 Km(RuBP) 와 Km($Co_2$) 값은 야생종 효소보다 상당히 크게 나타난 것인데 이는 변이의 결과로 효소에 대한 RuBP와 $Co_2$의 친화력이 감소된 때문이라고 생각한다. 이상의 결과는 변이체 효소의 큰 subunit의 구조유전자에 변화가 일어났고 따라서 이 변이의 유전은 non-Mendelian이라는 추리를 가능케 한다.
Ribulose-1, 5-bisphosphate carboxylase isolated from acetate requiring mutants, KX8215 and KX8261, of Chlamydomonas reinhardtii which were obtained by N-methyl-N-nitroso-N-nitrosoguanidine treatment have been characterized. Divalent metal cations, $Mg^{2+}$, $Ni^{2+}$, and $Co^{2+}$ appeared to enchance the enzyme activity whereas halogen anions, $Cl^-$, $I^-$, and $Br^-$ inhibited the enzyme activity. No difference between the mutant enzymes and that of the wild type has been detected in regards of ion effects, pH requirement, and the level of enzyme protein. Optimum temperature of the enzymes from both mutants were found to be higher at $35^{circ}C$ than at $25^{circ}C$ of the wild type enzyme. The specific activities of the mutant enzymes were remarkably lower than that of the wild type enzyme whereas Km (RuBP) and Km ($Co_2$) values of the former were significantly higher than those of the later, indicating that the affinities of the enzyme for RuBP and/or $Co_2$ are reduced as a result of the mutation. These results seem to support the previous indication that the lowered activities of the mutant enzymes would be due to the alteration in a structural gene for the large subunit in the enzymes and thus the inheritance of the mutation is non-Mendelian.
