Insights into the In Vivo Regulation of Glutamate Dehydrogenase from the Foot Muscle of an Estivating Land Snail

Table 2

Comparison of purified foot muscle GDH kinetic parameters from control and 10 day estivated Otala lactea assayed in the glutamate-utilizing direction. Data are means ± SEM, 𝑛≥3 independent purified preparations. 𝐾_𝑚 values were determined at optimal (i.e., those used to obtain 𝑉_max) cosubstrate concentrations. 𝐾_𝑎 values were determined at suboptimal substrate concentrations (identified in Section 2). ^aSignificantly different from the corresponding control value using the Student’s 𝑡-test, 𝑃<0.05. ^bSignificantly different from the same condition without ADP, 𝑃<0.05.

	Control	10-day estivated
𝐾𝑚 glutamate (mM)	0.90±0.02	0.84±0.02
𝐾𝑚 glutamate with 0.5 mM ADP (mM)	3.0±0.2^b	2.1±0.2^ab
𝐾𝑚 NAD^+ (mM)	0.59±0.08	0.49±0.02
𝐾𝑚 NAD^+ with 0.5 mM; ADP (mM)	0.159±0.005^b	0.191±0.009^b
𝐾𝑎 ADP (μM)	4.7±0.7	3.5±0.5
Fold activation with ADP	13.8±0.8	3.0±0.4^a
𝑉max (mU/mg)	9.4±0.8	30±1^a
𝑉max with 0.5 mM; ADP (mU/mg)	26.9±0.2^b	58±3^ab