Fitness

Phospholipase A

_{2}

(PLA

_{2}

) proteins are major components of snake venoms. When an animal is bitten by a venomous snake, these PLA

_{2}

enzymes catalyze the breakdown of phospholipids and can disrupt cell membranes, leading to muscle damage and other effects. Snake venoms often contain multiple types of PLA

_{2}

proteins, each with a slightly different amino acid sequence.

The pit viper Protobothrops flavoviridis contains multiple PLA

_{2}

enzymes, including BP-I and BP-II. The amino acid sequences of BP-I and BP-II differ by only one amino acid. A group of scientists tested the enzymatic activity of BP-I and BP-II over a range of concentrations. Their results are shown in Figure 1.

Based on the information provided above, which of the following statements is most likely true?

(Choice A)
With the exception of P. flavoviridis, a snake’s venom often contains a single type of PLA $_{2}$ ‍ enzyme so that its effect on prey is physiologically targeted.
(Choice B)
P. flavoviridis venom likely has a narrower range of physiological effects than a venom containing only BP-I.
(Choice C)
The active site of BP-I is slightly different from that of BP-II, so the two enzymes function differently at most concentrations.
(Choice D)
The amino acid difference between BP-I and BP-II causes BP-I to have a higher activity level than BP-II at medium and high concentrations.

Ohno, Motonori, Takahito Chijiwa, Naoko Oda-Ueda, Tomohisa Ogawa, and Shosaku Hattori. 2003. “Molecular evolution of myotoxic phospholipases A

_{2}

from snake venom.” Toxicon 42(841-54).

Shimohigashi, Yasuyuki, Ayako Tani, Hiroshi Matsumoto, Kin-ichi Nakashima, Yoko Yamaguchi, Naoko Oda, Yukio Takano, Hiro-o Kamiya, Junji Kishino, Hitoshi Arita, and Motonori Ohno. 1995. “Lysine-49-Phospholipases A

_{2}

from Trimeresurus flavoviridis venom are membrane-acting enzymes.” Journal of Biochemistry 118(1037-44).

AP®︎/College Biology

Course: AP®︎/College Biology > Unit 3

Problem