Question

included proper units when HLLL 1. The following kinetic data were generated for the enzyme SpB1, this enzyme has an unknown biological function. Using the information provided below answer questions la-le. All reactions had 0.1 mg/mL SPBT which based on amino acid sequence and gel filtration column chromatography has a molecular weight of 42,500 Daltons. S002- Substrate 1 Substrate 2 KM (MM) kcat (sec) glucose >50 <0.01 glucose NADP 4+1 0.5+0.07 glucose NAD 2718 2 +0.05 galactose >50 <0.01 galactose NADP 0.1 +0.03 19 +5 galactose NAD 0.9 +0.5 S6 + 2 0 oC la. What is the best substrate or substrates for this enzyme? Explain your conclusion here. (411 points) wold no w a mbini bas mencion and Ib. What can you classify "substrate 2" in the reaction as if this molecule gets converted into NADH or NADPH during the reaction and the SpB1 enzyme does not appear to be able to do the reverse reaction needed to regenerate NAD or NADPH? (2 points) -090 Ic. If you found a second form of the SpBl protein, called SpB1-2, and this second form has a ke/Km of 8.5 X 10/M-sec with the substrate or substrates you concluded in part 1a. Which form of SpBl would be the most efficient enzyme? Explain why. (4 points)

Answer 1

1-a) The best substrates for the enzyme are Galactose and NADP. This can be determined by the Km and Kcat values that are given. The ratio of   kcat/ Km gives the enzyme catalytic efficiency. Km is the substrate concentration at which half maximal velocity for enzyme catalysis is achieved, as per Michaelis-Menten reaction. kcat is the enzyme turnover number that gives the number substrate molecules converted by the enzyme to product in unit time. This ratio helps in determining the enzyme efficiency, considering the parameters like, affinity of the substrate, substrate binding etc. Since here, the  kcat/ Km ratio is the highest for galactose and NADP, they are the best substrate for the enzyme.

2-b) The substrate 2 may be considered as a limiting substrate since it marks a rate-limiting irreversible step and the product cannot be converted back to the original substrate for its regeneration.

3-c) The calculated  kcat/ Km ratio for the enzyme SpB1 was 24/0.07 (Highest value) whereas thatfor SpB1-2 is

8.5*105, which is much higher. Thus SpB1-2 would be a more efficient enzyme due to its significantly higher kcat/ Km ratio.